["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nIndividuals with Down syndrome (DS) exhibit altered body composition that could be assessed through bioelectrical impedance analysis (BIA). This study aims to compare the BIA measures and bioelectrical impedance vector analysis (BIVA) between individuals with and without DS.\n\n\nMethods\nWe evaluated 46 individuals with and 46 without DS through BIA and BIVA. We employed generalized linear models (GLM) to assess the effects of group and sex on BIA, adjusting by age and height.\n\n\nResults\nIndividuals with DS had lower whole‐body resistance/height (DS: 332.1 ± 51.1; non‐DS: 349.0 ± 57.5 Ω/m), reactance/height (DS: 36.4 ± 5.0; non‐DS: 41.9 ± 4.9 Ω/m) and impedance/height (DS: 334.1 ± 51.2; non‐DS: 351.4 ± 57.6 Ω/m), while men with DS showed lower phase angle (DS: 6.4 ± 0.7; non‐DS: 7.0° ± 0.5°) and lower bioimpedance index (DS: 50.8 ± 6.1; non‐DS: 55.2 ± 6.5 Ω/m2); men and women with DS had higher total body water (males p = 0.030; females p = 0.006) and intracellular water (males p = 0.020; females p = 0.010) compared with individuals without DS; women had lower extracellular water (males p = 0.090; females p = 0.004) compared with individuals without DS; the bioelectrical vectors for individuals with DS were different from the population ellipses (p < 0.050), and showed overhydration compared with non‐DS.\n\n\nConclusions\nAdults with DS showed a distinct hydration pattern in comparison with non‐DS adults, as shown in BIA and BIVA analysis.\n\n"]