In the immunocompromised patient, the pulmonary nodule remains a diagnostic and therapeutic challenge. We studied the incidence, cause, diagnosis, and therapy of pulmonary nodules after lung transplantation (LTx). Eight out of 64 patients (12.5%) developed pulmonary nodules after a median follow-up of 5.8 months (range, 1 to 10 months), The median age was 30.5 years (range, 21 to 62 years), Solitary pulmonary nodules (n = 2) disappeared spontaneously within 3 weeks and were suspected to be of infectious origin. The cause of multiple nodules (n = 6) was posttransplant lymphoproliferative disorder (PTLD [n = 3]), aspergillosis (n = 2), and abscesses caused by Pseudomonas aeruginosa and Staphylococcus aureus (n = 1). After an initial chest radiograph, CT with fine-needle biopsy was the most valuable diagnostic tool. In six patients, nodules resolved within 10 weeks (median, 8 weeks). Two patients, however, died of sepsis (P aeruginosa and S aureus and Aspergillus, respectively). The differential diagnosis of pulmonary nodules after LTx primarily comprises PTLD and infection (bacterial or fungal). To improve the outcome, early, aggressive treatment is mandatory; therefore, serial CT scans are strongly recommended to be part of the diagnostic armamentarium in LTx recipients.