We describe the case of a 67-year-old male patient with a moderately differentiated hepatocellular carcinoma (HCC) of the right liver lobe who underwent [ ¹⁸ F]fluorocholine positron emission tomography/computed tomography (PET/CT) for staging due to a suspicious lung lesion at previous CT scan. [ ¹⁸ F]fluorocholine PET/CT showed increased radiopharmaceutical uptake in a liver lesion corresponding to the known HCC. Furthermore, a right pulmonary hilar lesion suspicious for metastatic spread of HCC showed increased radiopharmaceutical uptake. Surprisingly, the histological assessment of the thoracic lesion demonstrated the presence of small cell lung cancer (SCLC). The patient underwent treatment with radiation therapy and chemotherapy for the SCLC and selective internal radiation therapy (SIRT) for the HCC. The patient died after one year due to progressive SCLC. This case demonstrates that coexisting tumors showing increased cell membrane turnover, including SCLC, can be detected by [ ¹⁸ F]fluorocholine PET/CT. In our case, [ ¹⁸ F]fluorocholine PET/CT findings influenced the patient management in terms of histological verification and different treatment of the detected lesions.