Reliability and validity of the Developmental Coordination Disorder Questionnaire (DCD-Q) was assessed using a population-based sample of 608 children (311 males, 297 females; mean age 7 y 8 mo [SD 2 y 4 mo]), a sample of 55 children with DCD referred to a rehabilitation clinic, and a control sample of 55 children matched for age and sex (48 males, seven females in each sample; mean age 8 y 3 mo [SD 2 y]). The DCD-Q is reliable and valid in the age range for which the questionnaire was developed(8 y-14 y 7 mo) and in a younger age range (4-8 y). Sensitivity and specificity of the DCD-Q was assessed using the Movement Assessment Battery for Children as the criterion standard. The DCD-Q met the standard for sensitivity (80%) in the clinic-referred sample (81.6%), but not in the population-based sample (28.9%). Specificity almost reached the standard of 90%: 89% in the population-based sample and 84% in the clinic-referred sample.