Abstract Introduction Lung mass is a common radiological finding among elderly. Bronchogenic carcinoma with metastases is the commonest cause of lung mass with multiple nodules in same or other lung seen in this age group. However, sometimes other uncommon malignancies with better prognosis can also present similarly. Primary pulmonary lymphoma is one of the rare malignancies, which have similar radiological presentation but different treatment and prognosis. Case presentation We present a non-smoking, elderly, diabetic man who presented with nonspecific symptoms of generalized weakness without any symptom pertaining to respiratory system. Examination of chest revealed findings suggestive of right lower lobe mass. On evaluation, he was found to have a well circumscribed lung mass on chest radiograph. Computerized tomography of chest with contrast showed a large mass involving right lung and multiple nodules in both lungs. For diagnosis, biopsy from right lung mass was done under image guidance. Histopathology revealed diffuse large B-cell non-Hodgkins lymphoma. Evaluation for primary malignancy leading to lung metastases was inconclusive. Patient was advised chemotherapy. Conclusion Primary pulmonary lymphoma is a rare disease and can present with non specific symptoms. Radiologically, it can easily be confused with commoner malignancies like, bronchogenic carcinoma with or without metastases. Primary pulmonary lymphoma carries different therapeutic and prognostic implications. Therefore, physicians should make every effort to achieve histopathological diagnosis before prognosticating patient presenting with lung mass.