The purpose of the study was to assess quality of life in patients with IDDM in relation to the type of insulin therapy. Two patient cohorts were studied. In cohort A, 77 patients deliberately intensified their traditional insulin injection therapy from up to two daily injections with syringe to multiple daily injections with insulin-pen; in cohort B, 55 patients changed from intensive therapy with pen to insulin pump-treatment (CSII). The therapeutic regimens were changed during a 5-day in-patient treatment and teaching course. The DCCT questionnaire was applied before and up to 6 months after changing of therapy. Treatment satisfaction increased after intensification of insulin therapy in both groups, mainly due to greater flexibility with leisure-time activities, and with the diet. Pump-users reported reduced problems with hypoglycemia (P < 0.02). HbA1c indicating acceptable metabolic control already before the study, remained unchanged. Therapy-associated inconvenience, mainly in association with lifestyle, improved in IDDM patients deliberately intensifying their insulin therapy by pens or pumps (CSII). Pump-treatment, rather than pen-therapy, conferred particular protection from hypoglycaemia.