Continuous subcutaneous insulin infusion (CSII) by insulin pump seems to improve glycemia and quality of life as compared to conventional insulin therapy in type 1 diabetes (T1DM). However, while many T1DM subjects achieve excellent glycemic control, some others cannot reach recommended goals. In a retrospective analysis, we searched for factors associated with glycemic control in T1DM patients treated with insulin pump therapy. Data from 192 patients (133 women and 59 men) treated with personal insulin pumps at the Department of Metabolic Diseases, University Hospital, Krakow, Poland were analyzed. Sources of information included medical records, memory read-outs from insulin pumps and data from glucose meters. Univariate, multivariate linear and logistic regression analysis for the association with hemoglobin A1c (HbA1c) level were performed. The mean age of the subjects was 28.9 (±11.2) years, the mean duration of T1DM-14.6 (±7.6) years, mean body mass index-23.5 (±3.1) kg/m2. The mean HbA1c level in the entire study group was 7.4% (57 mmol/mol). In the multivariate linear regression analysis, HbA1c correlated with the mean number of daily blood glucose measurements, number of hypoglycemic episodes per 100 blood glucose measurements, age at the examination, and continuous glucose monitoring system use. Multivariate logistic regression analysis for reaching the therapeutic target of HbA1c<7.0% (53 mmol/mol) showed that the independent predictors of achieving this goal included the same four variables. In a large clinical observation, we identified that patient-related and technological factors associated with glycemic control in adult pump-treated T1DM subjects.