This study investigated the 6-month prevalence rates of sleep-related problems and their association with daytime inadvertent napping, inattention, hyperactivity/impulsivity, and oppositional symptoms in children and adolescents. A representative school-based sample of 2463 first to ninth graders was recruited using a multistage sampling method. The instruments included the Sleep Habits Questionnaire (including dyssomnia, parasomnia, sleep schedules, and sleep-disordered breathing), the Chinese Health Questionnaire, and the Chinese versions of the Conners' Parent and Teacher Rating Scales-Revised: Short forms. The informants were mothers and teachers. The linear and nonlinear mixed models were used for statistical analyses and sex and age were controlled in the model. Results showed that the rates of middle insomnia, disturbed circadian rhythm, mouth breathing, and daytime inadvertent napping increased with age; whereas those of bedwetting, bruxism, sleep terrors decreased with age. Dyssomnia, sleep-disordered breathing problems, daytime inadvertent napping, and sleep schedules were related to attention-deficit/hyperactivity disorder (ADHD)-related symptoms as assessed by mothers' and teachers' ratings. Parasomnia was associated with ADHD-related symptoms as assessed by mothers' ratings. Our findings suggest an age trend of sleep problems similar to those found in the literature and the association of daytime inadvertent napping, inattention, hyperactivity/impulsivity, and oppositional symptoms with sleep-related problems.