Abstract. Simultaneous occurrence of lung cancer and pulmonary tuberculosis, as a significant cause of morbidity and mortality, appears in 0.7% of cases. The mechanisms of interaction between them are not fully clarified. We present a patient who, during the treatment of lung adenocarcinoma, developed pulmonary tuberculosis and, owing to a correct diagnosis, was provided with appropriate treatment. We analyzed the CT and radiographic findings during the follow-up of the patient and discussed the problems and doubts about the diagnosis of simultaneous occurrence of lung cancer and pulmonary tuberculosis. Differential diagnosis between tuberculosis and lung cancer is difficult and can pose a real clinical challenge due to the very similar symptomatology involving fever, malaise, sweating, and loss of body weight. Imaging methods routinely used in clinics, such as RTG, CT, and PET-CT, are of great help in such cases. The existence of the TB infection makes it difficult to adequately determine the nodal status in patients with lung cancer. The newly established lymph nodes may not only be the occurrence of tumors, but also already active tuberculosis or the progression of TB infection. Only the correct diagnosis can lead to successful treatment as described in this case.