diff --git a/ccm-cms/src/main/java/org/librecms/ui/AvailableDomainsListItem.java b/ccm-cms/src/main/java/org/librecms/ui/AvailableDomainsListItem.java
new file mode 100644
index 000000000..a13b48514
--- /dev/null
+++ b/ccm-cms/src/main/java/org/librecms/ui/AvailableDomainsListItem.java
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2021 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.librecms.ui;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public class AvailableDomainsListItem {
+
+    private String domainKey;
+
+    public String getDomainKey() {
+        return domainKey;
+    }
+
+    public void setDomainKey(final String domainKey) {
+        this.domainKey = domainKey;
+    }
+
+}
diff --git a/ccm-cms/src/main/java/org/librecms/ui/AvailableSitesListItem.java b/ccm-cms/src/main/java/org/librecms/ui/AvailableSitesListItem.java
new file mode 100644
index 000000000..705d64c11
--- /dev/null
+++ b/ccm-cms/src/main/java/org/librecms/ui/AvailableSitesListItem.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2021 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.librecms.ui;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public class AvailableSitesListItem {
+
+    private String uuid;
+
+    private String domainOfSite;
+
+    public String getUuid() {
+        return uuid;
+    }
+
+    public void setUuid(final String uuid) {
+        this.uuid = uuid;
+    }
+
+    public String getDomainOfSite() {
+        return domainOfSite;
+    }
+
+    public void setDomainOfSite(final String domainOfSite) {
+        this.domainOfSite = domainOfSite;
+    }
+
+}
diff --git a/ccm-cms/src/main/java/org/librecms/ui/PagesController.java b/ccm-cms/src/main/java/org/librecms/ui/PagesController.java
index 152df813c..092d13212 100644
--- a/ccm-cms/src/main/java/org/librecms/ui/PagesController.java
+++ b/ccm-cms/src/main/java/org/librecms/ui/PagesController.java
@@ -129,7 +129,7 @@ public class PagesController {
         @FormParam("primaryUrl") final String primaryUrlParam,
         @FormParam("categoryDomain") final String categoryDomainParam
     ) {
-        final Optional<Site> siteResult = siteRepo.findByDomain(siteParam);
+        final Optional<Site> siteResult = siteRepo.findByUuid(siteParam);
         if (siteResult.isEmpty()) {
             models.put("siteNotFound", true);
             models.put("site", siteParam);
@@ -152,6 +152,11 @@ public class PagesController {
         final Site site = siteResult.get();
         final Domain domain = domainResult.get();
         final String primaryUrl = primaryUrlParam;
+        
+        if (pagesRepo.findPagesForSite(primaryUrl).isPresent()) {
+            models.put("pagesInstanceAlreadyExisting", true);
+            return PAGES_LIST_TEMPLATE;
+        }
 
         pagesManager.createPages(primaryUrl, site, domain);
 
diff --git a/ccm-cms/src/main/java/org/librecms/ui/PagesTableModel.java b/ccm-cms/src/main/java/org/librecms/ui/PagesTableModel.java
index 296228684..1db824330 100644
--- a/ccm-cms/src/main/java/org/librecms/ui/PagesTableModel.java
+++ b/ccm-cms/src/main/java/org/librecms/ui/PagesTableModel.java
@@ -18,11 +18,16 @@
  */
 package org.librecms.ui;
 
+import org.libreccm.categorization.Domain;
+import org.libreccm.categorization.DomainRepository;
 import org.libreccm.security.AuthorizationRequired;
+import org.libreccm.sites.Site;
+import org.libreccm.sites.SiteRepository;
 import org.librecms.pages.Pages;
 import org.librecms.pages.PagesRepository;
 
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
 import javax.enterprise.context.RequestScoped;
@@ -41,12 +46,18 @@ import javax.transaction.Transactional;
 @Named("CmsPagesTableModel")
 public class PagesTableModel {
 
+    @Inject
+    private DomainRepository domainRepo;
+
     /**
      * Repository for pages.
      */
     @Inject
     private PagesRepository pagesRepo;
 
+    @Inject
+    private SiteRepository siteRepo;
+
     /**
      * Retrieves all available pages instances and builds a
      * {@link PagesTableRow} for each pages instance.
@@ -64,6 +75,31 @@ public class PagesTableModel {
             .collect(Collectors.toList());
     }
 
+    @AuthorizationRequired
+    @Transactional(Transactional.TxType.REQUIRED)
+    public List<AvailableSitesListItem> getAvailableSites() {
+        return siteRepo
+            .findAll()
+            .stream()
+            .filter(
+                site -> !pagesRepo.findPagesForSite(
+                    site.getDomainOfSite()
+                ).isPresent()
+            )
+            .map(this::buildSitesListItem)
+            .collect(Collectors.toList());
+    }
+
+    @AuthorizationRequired
+    @Transactional(Transactional.TxType.REQUIRED)
+    public List<AvailableDomainsListItem> getAvaiableCategoryDomains() {
+        return domainRepo
+            .findAll()
+            .stream()
+            .map(this::buildDomainsListItem)
+            .collect(Collectors.toList());
+    }
+
     /**
      * Helper method for building a {@link PagesTableRow} for a {@link Pages}
      * instance.
@@ -82,4 +118,21 @@ public class PagesTableModel {
         return row;
     }
 
+    private AvailableSitesListItem buildSitesListItem(final Site site) {
+        final AvailableSitesListItem item = new AvailableSitesListItem();
+
+        item.setDomainOfSite(site.getDomainOfSite());
+        item.setUuid(site.getUuid());
+
+        return item;
+    }
+
+    private AvailableDomainsListItem buildDomainsListItem(final Domain domain) {
+        final AvailableDomainsListItem item = new AvailableDomainsListItem();
+
+        item.setDomainKey(domain.getDomainKey());
+
+        return item;
+    }
+
 }