Crohn’s disease is a chronic inflammatory disease of the gastrointestinal tract. Detection of disease activity and location of Crohn’s disease along the gastrointestinal tract are of crucial importance for diagnosis and management of the disease. The study presents 3 patients with Crohn’s disease, who were referred for a combination of positron emission tomography and computed tomography (PET/CT) using 18-F fluorodeoxyglucose (FDG). Results of the PET/CT closely correlated with Crohn’s disease activity index (CDAI), results of the endoscopic examination and magnetic resonance enteroclysis. FDG PET/CT examination could be useful in assessing the extent and activity of inflammation in the digestive tract in patients with Crohn’s disease.