Attention-deficit/hyperactivity disorder (ADHD) and enuresis co-occur at a higher rate than expected; the cause for this is unclear.Diagnostic and demographic variables were compared in 344 children ages 6 to 12 years, with and without enuresis, recruited in an ADHD genetic study. Sleep variables were investigated in a subgroup of 44 enuretic children with age- and sex-matched nonenuretic controls. The association of enuresis with single nucleotide polymorphisms located in regions reported in linkage with enuresis was explored.The prevalence rate of nocturnal enuresis was 16.9% for the entire cohort. There were no differences in sex, age, socioeconomic status, intelligence quotient, medication treatment, or comorbidities. The enuresis group had a higher likelihood of inattentive symptoms than the nonenuretic group. Night wakings and ability of children to wake themselves in the morning were both significantly decreased in children with enuresis compared with control children in the Child Sleep Habits Questionnaire Night Wakings subscale. No significant association was found with chromosomal regions previously reported in linkage with enuresis.Deficits in arousal may contribute to both enuresis and inattentive ADHD. Nocturnal enuresis may be a useful clinical marker in identifying a subgroup of the inattentive phenotype in ADHD genetic studies.