Objective. The aim of this study was to assess the body composition and nutritional status of children and adolescents with newly diagnosed type 1 diabetes by using bioelectrical impedance analysis (BIA) with phase angle (PA) calculation. PA is considered to be the most sensitive indicator of the nutritional and functional status and it has not been evaluated in such population yet. Research Design and Methods. 63 children and adolescents aged 4 to 18 years, with newly diagnosed type 1 diabetes, were included in the study. Control group consisted of 63 healthy children and adolescents, without diabetes or other chronic disease having impact on the nutritional status, strictly matched by gender and age in a 1:1 case-control manner. In both groups a BIA was performed and PA was calculated. Results. Diabetic patients had highly significantly lower PA, 4.85 ± 0.86 vs. 5.62 ± 0.81 respectively, P<0.001 compared to control subjects. Also lower percentage of body cell mass (BCM%), 46.89 ± 5.67% vs. 51.40 ± 4.19% respectively, P<0.001, lower body cell mass index (BCMI), 6.57 ± 1.80% vs. 7.37 ± 1.72% respectively, P=0.004 and lower percentage of muscle mass (MM%), 44.61 ± 6.58% vs. 49.40 ± 7.59% respectively, P<0.001, were found in diabetic group. Conclusions. The lower PA score together with lower MM%, BCM% and BCMI in diabetic patients indicate their worse nutritional and functional status compared to healthy subjects. To assess the predictive and prognostic value of these findings further prospective studies in this population are required.