BACKGROUND: This study quantified the risk of urinary bladder neoplasms in cancer patients taking into account the age at first diagnosis, the gender of the patients and the lead time between diagnoses. METHODS: We used standardised incidence ratios (SIRs) to compare the incidence of bladder tumours in 967 767 cancer patients with the incidence rate in the general Swedish population. A total of 3324 male and 1560 female patients developed bladder tumours at least 1 year after first cancer diagnosis. RESULTS: After bladder and renal pelvis cancers, the SIRs of bladder neoplasms were higher in female than in male patients. Men affected by lung, stomach and larynx tumours belonged to the population at high risk for bladder cancer. Treatment of breast, ovarian and cervical cancers seems to contribute to the subsequent development of bladder neoplasms. Long latencies (16-25 years) were observed after testicular, cervical and endometrial cancers. Detection bias had an important role after prostate cancer. Chemotherapy with cyclophosphamide and cisplatin, and also radiotherapy, seem to increase the risk of subsequent neoplasms in the bladder. CONCLUSIONS: These population-based results may help urologists to assess the risk of bladder neoplasms in cancer survivors. Our data should guide ongoing studies that investigate the effectiveness of bladder cancer screening in cancer patients.