Background. Autosomal dominant polycystic kidney disease (ADPKD) is a systemic hereditary disorder characterized by bilateral diffuse renal cysts. Extrarenal involvement is a well known manifestation of ADPKD. Data relating to the association between seminal vesicle cysts and ADPKD are limited. The aims of this study are to evaluate the frequency of seminal vesicle cysts in ADPKD and to assess the relationship between seminal vesicle cysts, with cysts in the liver and prostate, and creatininaemia. Methods. Forty five male patients (mean age 40 years, range 13-67) were included in the study. Each subject underwent a formal interview, physical examination; and abdominal and transrectal ultrasonography. Three patients were infertile, but one of the patients also had varicocele. Results. Seminal vesicle cysts were present in 27 (60%) patients. Liver and prostate cysts were present in 19 (42%) and five (11%) patients, respectively. There was a positive correlation between seminal vesicle cysts, cysts in the liver, and serum creatinine concentrations. Conclusion. Our conclusions are: (i) seminal vesicle cysts are not uncommon in ADPKD; (ii) ADPKD should be looked for in patients with seminal vesicle cysts, and (iii) the clinical significance of seminal vesicle cysts in ADPKD remains to be defined.