Rationale:Differentiation of benign and malignant lesions in the head of pancreas is the key. When the mass is small, it is difficult to distinguish via conventional imaging modalities. Positron emission tomography and magnetic resonance imaging (PET/MRI) can distinguish benign and malignant lesions from the perspective of metabolism, which provides a new idea for the diagnosis of pancreatic head mass.Patient concerns:We report the case of a 44-year-old male patient who underwent an18F-fluorodeoxyglucose PET/MRI for medical examination. The patient did not complain of special discomfort.Diagnoses:PET-MRI revealed in the head of the pancreas, there is a circular space-occupying lesion without obvious fluorodeoxyglucose accumulation, which tends to be benign based on its MRI and metabolic characteristics.Interventions:The patient refused further laboratory examination or ultrasound gastroscopy as there is no discomfort.Outcomes:No special discomfort was found in the patient after 6 months follow-up.Lessons:If routine examination fails to diagnose benign or malignant pancreatic head occupying, and the patient refuses invasive examination, PET-MRI can be performed for identification.