Children born small for gestational age (SGA) with a poor adult height (AH) expectation benefit from treatment with GH and additional gonadotropin-releasing hormone analog (GnRHa). Because both SGA birth and GnRHa treatment might negatively influence cognition, health-related quality of life (HRQoL), and psychosocial functioning, we assessed these outcomes at AH. A randomized, dose-response GH study until AH involving 99 adolescents born SGA, of whom 61 children received 2 additional years of GnRHa treatment. At AH, the Wechsler Adult Intelligence Scale and TNO-AZL Adults Quality of Life questionnaire were administered to the study group. Additionally, the study group and 67 adolescents born SGA (19 GnRHa) from a second study group completed the Self-Perception Profile of Adolescents and Child/Adolescent Behavior Checklist at AH. Scores in GH-treated young adults with GnRHa treatment (GH/GnRHa group) were compared with GH-treated adolescents without GnRHa treatment (GH group) and a reference population. Mean age (SD) at AH was 17.5 (1.2) and 17.4 (1.4) years in the GH/GnRHa and GH group, respectively. Intelligence quotient scores were similar in GH/GnRHa and GH groups (96.33 vs 92.47). HRQoL was similar between both groups and also when compared with the reference population, but the GH/GnRHa group had a significantly lower perception of cognitive functioning. Self-perception and problem behavior were similar in the GH/GnRHa and GH groups. AH did not correlate with HRQoL, self-perception, or problem behavior. Combined GH/GnRHa treatment has no long-term negative effects on cognition, HRQoL, self-perception, and behavior in early adulthood, compared with GH treatment only.