Background: In the past, overtreatment may have resulted in growth impairment in patients with phenylketonuria. Objective: The paper aims to investigate height and body composition in early treated patients with phenylketonuria who were diagnosed between 1981 and 2008. Design: A cross-sectional study of 89 patients with phenylketonuria and 78 controls aged (mean. ±. SD, in years) 14.4. ±. 6.6 and 15.9. ±. 7.1, respectively, was undertaken, including anthropometric and body composition evaluation using bioelectrical impedance. Median Phe concentrations in the last year before study enrolment were used as a measure of metabolic control. Natural protein and amino acid mixture intakes were recorded in patients. Results: No statistically significant differences were found on height z-scores between patients and controls aged less than 19. years (p. = 0.301), although all patients with classical phenylketonuria revealed negative height z-scores, resulting in a mean. ±. SD of -. 0.65. ±. 0.41. Among participants aged 19. years or more, median (p25-p75) of height was significantly higher in controls [168.0. cm (159.2-174.8)] than in patients [160.5. cm (151.9-167.5)] (p. = 0.017). No significant differences were found between patients and controls regarding fat mass, fat free mass, muscular mass, body cell mass index and phase angle. Conclusion: Our results suggest that early and continuously treated patients with phenylketonuria born after 1992 can achieve normal growth and body composition, although the negative height z-score in patients with classical phenylketonuria strengthens the continuous need to optimize the quality of their protein intake. © 2013 Elsevier Inc.