diff --git a/hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/ExistsSubqueryForeignKeyTest.java b/hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/ExistsSubqueryForeignKeyTest.java
new file mode 100644
index 0000000000..eeae5fb4f7
--- /dev/null
+++ b/hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/ExistsSubqueryForeignKeyTest.java
@@ -0,0 +1,110 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.query.hql;
+
+import org.hibernate.dialect.HSQLDialect;
+
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.Jira;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SkipForDialect;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.Tuple;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Marco Belladelli
+ */
+@DomainModel(annotatedClasses = {
+		ExistsSubqueryForeignKeyTest.Person.class,
+		ExistsSubqueryForeignKeyTest.Document.class,
+})
+@SessionFactory
+@SkipForDialect(dialectClass = HSQLDialect.class, reason = "HSQLDB doesn't like the case-when selection not being in the group-by")
+@Jira( "https://hibernate.atlassian.net/browse/HHH-18816" )
+public class ExistsSubqueryForeignKeyTest {
+	@Test
+	public void testWhereClause(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			final Long result = session.createQuery(
+					"select count(*) from Document d join d.owner o "
+							+ "where exists(select p.id from Person p where p.id = o.id) group by o.id",
+					Long.class
+			).getSingleResult();
+			assertThat( result ).isEqualTo( 1L );
+		} );
+	}
+
+	@Test
+	public void testSelectCaseWhen(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			final Tuple result = session.createQuery(
+					"select case when exists(select p.id from Person p where p.id = o.id) then 1 else 0 end,"
+							+ "count(*) from Document d join d.owner o group by o.id",
+					Tuple.class
+			).getSingleResult();
+			assertThat( result.get( 0, Integer.class ) ).isEqualTo( 1 );
+			assertThat( result.get( 1, Long.class ) ).isEqualTo( 1L );
+		} );
+	}
+
+	@BeforeAll
+	public void setUp(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			final Person person1 = new Person( 1L, "person_1" );
+			session.persist( person1 );
+			session.persist( new Document( 1L, "doc_1", person1 ) );
+		} );
+	}
+
+	@AfterAll
+	public void tearDown(SessionFactoryScope scope) {
+		scope.getSessionFactory().getSchemaManager().truncateMappedObjects();
+	}
+
+	@Entity(name = "Person")
+	static class Person {
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Person() {
+		}
+
+		public Person(Long id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+	}
+
+	@Entity(name = "Document")
+	static class Document {
+		@Id
+		private Long id;
+
+		private String title;
+
+		@ManyToOne
+		private Person owner;
+
+		public Document() {
+		}
+
+		public Document(Long id, String title, Person owner) {
+			this.id = id;
+			this.title = title;
+			this.owner = owner;
+		}
+	}
+}