Abstract Background Despite significant progress in managing cancer in children, adolescents, and young adults (CAYAs), persistent complications impact their quality of life with some being severe or life-threatening.(1,2) Long-term outcomes depend on common risk factors for malignancy and cardiovascular diseases (CVD) that overlap, and treatments are known to increase the risk for CVD. (3,4) Healthcare inequality due to socioeconomic status is omnipresent and may significantly impact outcomes. Purpose This study aims to comprehensively cover morbidity, mortality, demographic, and socioeconomic factors among CAYAs and investigate their impact on cardiovascular outcomes. Methods This retrospective matched cohort study included the entire Swedish population under 25 with cancer from 1958 to 2021. The study population was identified from the National Board of Health and Welfare's Cancer Register, with controls paired 1:5 based on age, sex, and residence. Multiple registers provided data on morbidity, mortality, and demographics. Results Covering 63 years, identified 65,173 CAYAs (1.24 million patient-years) and matched with 312,935 controls (7.45 million person-years), a total of 378,108 individuals (74% females). The mean follow-up was 19.5 (SD16.9) years for CAYAs, and 23.8 (16.8) for controls, (p<0.001). At the end of the study, the median age of CAYAs was 33.4 (IQR 27.9) years and controls 39.2 (28.3) (p<0.0001), with an age span of <1-88 years in both groups. CVD was detected in 16.9 % of the CAYAs, representing a 1.21-time elevated risk (95% CI 1.18-1.23, p<0.0001) compared to controls. CAYAs had a higher mortality rate, and 5-years survivors lived a mean of 26.9 years shorter than controls. CV mortality was also increased in CAYAs, (1.9% compared to 0.7% in controls) but at a higher age, although at a mean of 22.8 years younger than their controls. The 5-year survivors were older at CV mortality and lived in mean 6.5 years shorter than controls (p<0.0001). After adjusting for socioeconomic factors, individuals born outside Europe and those with greater sick leave had a higher mortality risk, while education and marriage showed a beneficial association with mortality. (p<0.0001). Interpretation The Rebuc study, spanning six decades, revealed a significantly increased risk of serious complications among young cancer patients in Sweden. Not only do young cancer patient survivors face a significantly higher risk for cardiovascular disease, but the higher mortality risk before middle age also underscores the severity of the health challenges they confront. Furthermore, these young individuals are more susceptible to socioeconomic factors that may adversely affect their survival.