The purpose of this study is to investigate the usefulness of a 20-minute brief mindfulness meditation in positively affecting mood and attention. Its effects were compared with the effects from a period of distraction and a control condition. The sample consisted of 63 veterans with Posttraumatic Stress Disorder. Pre-post test of the State-Trait Anxiety Inventory and the Positive and Negative Affect Schedule were used to assess levels of state anxiety and mood. The Stroop Task was employed as a measure of selective attention. A one-way analysis of variance and split-plot analysis of variance were conducted. To control high comorbidity within this sample, sub-analyses were conducted excluding participants with other psychological or physical conditions. The results revealed that meditators without sleep problems indicated greater selective attention levels. A negative mood decrease was found in all participants regardless of the intervention group assignment. Implications for research and practice were discussed.