Bleomycin is an antineoplastic agent causing fatal pulmonary toxicity. Early diagnosis of bleomycin-induced pneumonitis is crucial to prevent irreversible damage. Pulmonary function tests are unreliable for identifying risk of bleomycin toxicity. Fluorodeoxyglucose PET/CT scanning can reveal inflammation secondary to pneumonitis but is not sufficiently specific for diagnosis. We retrospectively analyzed scans from 77 patients with Hodgkin lymphoma (median age 41 years, mean bleomycin dose 134 mg) to evaluate bleomycin-induced pneumonitis. We identified 13 patients with abnormal lung uptake of fluorodeoxyglucose. Tracer activity was predominantly diffuse, bilateral, in the lower lobes and subpleural areas. Interim scanning during treatment revealed pneumonitis in eight of 13 patients (asymptomatic in six). One asymptomatic patient died of bleomycin toxicity. For remaining 12 patients, bleomycin was discontinued and methylprednisolone given, all showed resolution of the pneumonitis. These findings suggest that routine interim or end-of-treatment FDG-PET/CT scanning could be beneficial for alerting clinicians to asymptomatic bleomycin-induced toxicity.