We conducted a population-based retrospective study to assess the long-term risks of overall and cause-specific mortality and second malignant neoplasm (SMN) among survivors of young adult cancer compared to the risk in British Columbia (BC) population and to evaluate the effects of demographic and clinical factors on risk. 1248 5-year survivors of young adult cancer diagnosed 1970-1995 between 20 and 24 years of age were identified from the BC Cancer Registry and followed to the end of 2007. Standardized mortality ratios (SMRs) and standardized incidence ratios (SIRs) were calculated. The Cox proportional hazards model was used to estimate the effects of different demographic and disease-related characteristics on the risk of death and SMN. A total of 138 deaths and 62 SMNs were observed during follow-up. The overall SMR was 5.9 (95% CI 4.9-6.9) and the absolute excess risk was 5.3 per 1,000 person-years. The overall SIR was 3.0 (95% CI 2.3-3.8). Treatment with radiation resulted in increased risks of death and SMN. These observed increased risks emphasize the importance of prevention, surveillance, and treatment of late effects in survivors of young adult cancers.