Objectives: To determine the underlying factor structure of diabetes specific support using a modified diabetes family social support questionnaire, the M-DSSQ-Family, in one half of a sample of adolescents with type 1 diabetes, confirm it in the second half, test invariance in factor structure across gender and age, and test the reliability of the resulting scales. Method: The study included 11-19 yr old youngsters with type 1 diabetes, who are all on daily insulin injection or pump. A total of 437 adolescents (54.5% girls; mean age 14.7 yr; mean diabetes duration 6.1 yr) participated in the study. Results: Exploratory factor analyses in the first half of the random sample suggested five factors including 45 items with loading ≥0.40 and explaining 40% of item variance. Confirmatory factor analysis in the remainder of the sample showed good indices of fit with exclusion of only five items. The final model with five underlying factors including 'Guidance and Supervision (10 items, α = 0.84)', 'Encouragement of Self-care and Exercise (8 items, α = 0.82)', 'Support in Critical Situations (6 items, α = 0.90)', 'Nourishment (9 items, α = 0.84)', and 'Emotional Support (7 items, α = 0.81)' was confirmed across gender and age. In a second order factor analysis, all five factors loaded on one overall factor Diabetes Social Support-Family (α = 0.93). Conclusion: The 40-item M-DSSQ-Family presented a different view of traditional aspect of diabetes social support from family which may be more fruitful for adolescents. In addition, it emerged as a valid and reliable measure of family support for Dutch adolescents with type 1 diabetes. © 2011 John Wiley & Sons A/S.