OBJECTIVE Little is known about right ventricular (RV) function in survivors of childhood cancer, although both anthracyclines and radiotherapy represent potentially cardiotoxic treatment. We hypothesized that adult survivors of childhood malignant lymphoma or acute lymphoblastic leukaemia would have impaired RV function. RESULTS We examined RV dimensions and function by echocardiography in 246 survivors, mean 21.7 years after diagnosis, and in 211 matched controls. Of the survivors, 84% had been exposed to anthracyclines, mediastinal radiotherapy, or both. Compared with controls, all mean measures of RV function were lower in the survivor group: fractional area change (44.5 vs. 48.6%, P < 0.001), tricuspid annular plane systolic excursion (2.24 vs. 2.49 cm, P < 0.001), peak systolic tricuspid annular velocity (12.1 vs. 13.0 cm/s, P < 0.001), and free wall strain (-26.5 vs. -28.4%, P < 0.001). In contrast, there were little differences in RV diastolic dimensions. Lower measures of RV function were found in all survivor subgroups having received cardiotoxic treatment, but not in the 16% of survivors unexposed to anthracyclines or mediastinal radiotherapy. Signs of RV systolic dysfunction were found in 30% of the survivors, and more than 3 times more often in survivors with left ventricular dysfunction. CONCLUSIONS Long-term survivors of childhood lymphoma or acute lymphoblastic leukaemia frequently have impaired RV function compared with controls. As this is associated with increased risk of heart failure and death in many other conditions, we recommend increased attention to RV function in childhood survivors. Whether RV dysfunction impairs prognosis in this patient group should be examined in longitudinal studies.