Background: The present study aimed at investigating long-term mortality of patients who underwent solid organ transplantation during childhood and at identifying their causes of death. Methods:A cohort of 233 pediatric solid organ transplant recipients who had a kidney, liver, or heart transplantation between 1982 and 2015 in Finland were studied.Year of birth-, sex-, and hometown-matched controls (n = 1157) were identified using the Population Register Center registry. The Causes of Death Registry was utilized to identify the causes of death.Results: Among the transplant recipients, there were 60 (25.8%) deaths (median follow-up 18.0 years, interquartile range of 11.0-23.0 years). Transplant recipients' risk of death was nearly 130-fold higher than that of the controls (95% CI 51.9-1784.6).The 20-year survival rates for kidney, liver, and heart recipients were 86.1% (95% CI 79.9%-92.3%), 58.5% (95% CI 46.2%-74.1%), and 61.4% (95% CI 48.1%-78.4%), respectively. The most common causes of death were cardiovascular diseases (23%), infections (22%), and malignancies (17%). There were no significant differences in survival based on sex or transplantation era. Conclusion:The late mortality is still significantly higher among pediatric solid organ recipients in comparison with controls. Cardiovascular complications, infections, and cancers are the main causes of late mortality for all studied transplant groups. These findings emphasize the cruciality of careful monitoring of pediatric transplant recipients in order to reduce long-term mortality.