Background: Fluorodeoxyglucose (FDG) positron emission tomography (PET) is emerging as an important noninvasive investigation in benign pulmonary conditions too. The aim of this study was to investigate its utility in the diagnosis and monitoring of various benign pulmonary diseases. Methods: In this prospective observational hospital-based study 50 consecutive patients (26 males) with benign lung diseases underwent computed tomography of chest followed by FDG-PET at baseline and after treatment where appropriate. The findings of FDG scan are reported in the context of clinical, histopathological, physiological and radiological findings. Results: All patients showed increased FDG uptake in the lung corresponding to CT findings. Of the 9 patients with sarcoidosis stage 1 (n=1), stage 2 (n=3) and stage 3 (n=5), additional uptake in the myocardium and thyroid was noted in two patients which resulted in a change in the modality of treatment. Repeat FDG scan post-treatment showed decreased uptake in all patients which was consistent with clinico-radiologic, microbiological or spirometry findings. Increased uptake was seen in one patient with pulmonary tuberculosis (TB) and in one patient with TB mediastinal lymphadenopathy at the end of intensive phase discordant with clinical and microbiological response. Of nine cases of idiopathic interstitial pneumonias (IIPs), additional intense FDG uptake was found in two cases which corresponded to the areas of honeycombing. Conclusions: FDG-PET scan can be used as an important adjunct non-invasive investigation in diagnosing and monitoring of various benign lung conditions. It also helps in assessing whole body disease burden which may change therapeutic decisions.