To evaluate the impact of reduced radiation and combined modality therapy (CMT) in the treatment of Hodgkin lymphoma, we assessed the risk of second malignant neoplasms (SMNs) in patients who received extended-field radiotherapy only and patients who underwent CMT. Among 404 patients treated at Yale during 1970–2004, the risk of solid SMNs was elevated in the radiotherapy only group (n = 198, median follow-up = 21·1 years) compared to the general population, with a standardized incidence ratio (SIR) of 1·85 [95% confidence interval (CI): 1·17–2·78]. No increase was observed in the CMT group (n = 206, median follow-up = 14·3 years), although potential differences in SMN risk were indicated across the age spectrum in subgroup analysis. Patients who received mustard-containing regimens had increased risks for haematological SMNs (SIR = 8·74) and all SMNs (SIR = 1·85). When the analysis was stratified by age at diagnosis, children (0–20 years) had a significantly higher risk of SMNs (SIR = 5·24, 95% CI: 2·26–10·33), regardless of the treatment received. These findings suggest that recent treatment options utilizing lower dose radiation and less intense alkylator chemotherapy might be associated with lower incidences of SMNs among adults but not necessarily children.