This study assessed stability of measurement of quality of life (QOL) and health-related quality of life (HRQOL) over the course of 1 year among 185 adolescents (mean age 16y, SD 1y 9mo) with cerebral palsy (CP). Participants were classified on the Gross Motor Function Classification System as level I (n=55), II (n=30), III (n=27), IV (n=46), or V (n=27). QOL was assessed by self- (n=125) or proxy-report (n=60) with the Short Version of the Quality of Life Instrument for People with Developmental Disabilities (QOL Instrument), which describes domains of Being, Belonging, and Becoming. HRQOL was captured through parent proxy-reports with the Health Utilities Index Mark 3 (HUI3). Generalizability coefficients (G) for domain and Overall QOL scores on the QOL Instrument ranged from 0.50 to 0.73, indicating that between 50 and 73% of the variance was stable over 1 year. Stability on the HUI3 was excellent (G>0.90) for ambulation and overall utility scores; moderate (G=0.70–0.90) for speech, vision, dexterity, cognition, and hearing; and low for pain (G=0.48) and emotion (G=0.24). Correlations between scores on the two instruments were moderate even when adjustments were made for the lack of perfect stability over 1 year. This supports the notion that QOL and HRQOL are different aspects of life experience among adolescents with CP.