(a) Evaluate the efficacy and duration of effect of lisdexamfetamine dimesylate (LDX) in adult ADHD. (b) Assess the reliability and validity of the Adult ADHD Medication Smoothness of Effect Scale (AMSES) and Adult ADHD Medication Rebound Scale (AMRS). Adults (N = 40) with ADHD were treated with LDX for up to 12 weeks. The primary efficacy measure was the ADHD Rating Scale (ADHD-RS). The psychometric properties of the AMSES and AMRS are analyzed and compared with the ADHD-RS, ADHD Self-Report Scale (ASRS) v1.1 Symptom Checklist, and Time-Sensitive ADHD Symptom Scale (TASS). ADHD-RS scores were significantly improved with LDX. The AMSES and AMRS had high internal consistency and were correlated with the ADHD-RS, ASRS v1.1 Symptom Checklist, and TASS. LDX is effective in treating adult ADHD and has a smooth drug effect throughout the day with limited symptom rebound. The AMSES and AMRS are valid and reliable measures.