diff --git a/diagnose-plesk.sh b/diagnose-plesk.sh
new file mode 100755
index 0000000..d16ea5d
--- /dev/null
+++ b/diagnose-plesk.sh
@@ -0,0 +1,53 @@
+#!/bin/bash
+
+echo "=== PLESK DIAGNOSTIC SCRIPT ==="
+echo ""
+
+# Source libraries
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/lib/common-functions.sh"
+source "$SCRIPT_DIR/lib/system-detect.sh"
+source "$SCRIPT_DIR/lib/domain-discovery.sh"
+source "$SCRIPT_DIR/lib/user-manager.sh"
+
+echo "1. System Detection:"
+echo "   Control Panel: $SYS_CONTROL_PANEL"
+echo "   OS: $SYS_OS_TYPE $SYS_OS_VERSION"
+echo ""
+
+echo "2. Testing list_all_users():"
+users=$(list_all_users)
+user_count=$(echo "$users" | grep -v "^$" | wc -l)
+echo "   Found $user_count users"
+echo "   Users: $users"
+echo ""
+
+echo "3. Testing list_all_domains():"
+domains=$(list_all_domains)
+domain_count=$(echo "$domains" | grep -v "^$" | wc -l)
+echo "   Found $domain_count domains"
+echo "   Domains: $domains"
+echo ""
+
+echo "4. Check if plesk command exists:"
+which plesk
+echo ""
+
+echo "5. Check if plesk bin user --list works:"
+/usr/local/psa/bin/user --list 2>&1 || echo "FAILED"
+echo ""
+
+echo "6. Check if plesk bin site --list works:"
+/usr/local/psa/bin/site --list 2>&1 || echo "FAILED"
+echo ""
+
+echo "7. Check plesk-helpers.sh sourced:"
+type plesk_list_domains 2>&1 || echo "plesk_list_domains NOT FOUND"
+type plesk_list_users 2>&1 || echo "plesk_list_users NOT FOUND"
+echo ""
+
+echo "8. Check /var/www/vhosts directory:"
+ls -la /var/www/vhosts/ 2>&1 | head -20
+echo ""
+
+echo "=== END DIAGNOSTIC ==="