A 60-year-old Laotian man who had presented with cough and chest pain was referred to our hospital. A chest computed tomography (CT) scan showed a mass shadow on the left upper lobe, and ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) CT revealed increased FDG uptake in the lesion. Although lung cancer was strongly suggested, transbronchial biopsy of the mass showed only eosinophilic infiltration. Detailed history taking revealed that he had eaten raw crabs. Although no Paragonimus ova or worms were detected by bronchoscopy, immunological tests showed that his serum contained specific antibodies against paragonimiasis antigens, and he was therefore diagnosed with paragonimiasis by serology. A shadow with histopathologically detected eosinophilic infiltration is suggestive of paragonimiasis, although it is difficult to differentiate it from lung cancer when there is increased FDG uptake in the lesion. It is important to take a detailed history including travels and meals. Immunological tests are useful for diagnosing paragonimiasis.