Advances in medical technology, including insulin pump therapy, have not led to the expected improvement in glucose control of type 1 diabetes, especially in late adolescents and young adults. Objectives. The aim of the study was to evaluate metabolic control in insulin pump therapy (IPT) in late adolescents and young adults with type 1 diabetes mellitus. Material and Methods. The study was conducted in 86 subjects with type 1 diabetes, and included 45 patients aged 16–19 years (mean 17.6±1.2) treated in a pediatric outpatient clinic and 41 subjects aged 19–26 years (mean 22.8±2.2) treated in an adult outpatient clinic of the same university hospital, who received the same refund of IPT. Results. Late adolescents had a lower BMI (22.7±2.9 kg/m2 vs. 24.2±3.2 kg/m2; P<0.05), higher HbA1c (69.4±15.1 mmol/mol vs. 58.5±11.8 mmol/mol; P<0.001) and mean blood glucose levels (10.4±2.6 mmol/l vs. 9.2±1.4 mmol/l, P<0.05), and received higher insulin doses per day (0.85±0.23 IU/kg vs. 0.65±0.13 IU/kg; P<0.001). The mean diabetes and IPT duration, number of visits, basal/bolus insulin ratio, number of insulin boluses, blood glucose tests and the episodes of hypoglycemia were similar. Conclusions. Metabolic control in late adolescents with type 1 diabetes on IPT  is significantly worse than in young adults, despite higher doses of insulin and very similar way of treatment and self-control. This may be related to the patients age or the less rigorous approach to therapeutic recommendations resulting from pediatric diabetes care.