BACKGROUND Lung transplant recipients (LTR) are at increased risk for squamous cell carcinoma of the skin (SCC), but risk factors (RF) are incompletely understood. OBJECTIVE To assess associations between exposure to certain medications and viral infections, and subsequent SCC development. METHODS Retrospective study examining incidence and potential RF for SCC in LTR transplanted from 1992 to 2010 followed up at one centre. Cumulative incidence and Cox proportional hazards regression models were used to evaluate RF in the first year post-transplant for SCC formation during the follow-up. RESULTS In 205 analysed LTR, 46 patients were diagnosed with SCC during a median follow-up of 4.9 years. The cumulative incidences of first SCC were 16.7% and 34.1%, for 5 and 10 years post-transplantation respectively. Multivariable analysis identified CMV replication (HR 7.69, 95% CI 2.93-20.2, P < 0.001) and moxifloxacin exposure (HR 2.35, 95% CI 1.15-4.81, P = 0.020) during the first year post-transplantation as independent RF for SCC development during follow-up. CONCLUSION In our cohort, moxifloxacin use and CMV replication during the first year post-transplantation were associated with increased risk for SCC. These two factors could be indicators of over-immunosuppression. Their role in SCC development requires investigations in larger cohorts and prospective studies.