Recent advances in medical and nursing care have improved the prognosis of patients with severe motor and intellectual disabilities (SMID). However,there has been a proportionate increase in the incidence of malignant tumor-related deaths in this population owing to their prolonged survival. In this study,we reviewed the clinical characteristics of four bladder cancers in young SMID patients treated at our hospital. In all patients,a diagnosis of a bladder tumor was made after a referral from the family medical department to the urology department ; the median time from the first symptom to the diagnosis was 12.5 months (range : 0-17 months). In clinical staging,two patients had non-invasive cancer,while the other two had invasive bladder cancer (one patient with cN1). Radical cystectomy with ileal conduit was performed in three patients (pathological stages were pTa with CIS,pT3aN1,and pT3bN0),and transurethral bladder tumor ablation was performed in the fourth one. The median postoperative follow-up period was 134 months (range : 20-182 months). Three patients survived afterward,while one patient died due to other causes. These findings suggest that young SMID patients tend to have a more severe form of bladder cancer compared to the general young population. Therefore,complaints of gross hematuria and urinary symptoms in young patients with SMID need appropriate evaluation in cooperation with the family department for an early diagnosis.