This study investigated the effects of mindfulness training on the behavior of four 8-year-old boys with attention-deficit/hyperactivity disorder. A multiple baseline design was used to investigate whether a multisession mindfulness intervention resulted in increased on-task behaviors in the classroom. Graphic analysis of observation data indicated that the intervention was effective in increasing the percentage of intervals of on-task behavior. In addition, parent and teacher ratings on the Behavior Assessment System for Children, 2nd Edition (BASC-2) generally indicated a decrease in hyperactive behaviors. Conversely, significant changes in pre- and posttest ratings on the BASC-2 Attention Problems Scale were generally not observed.