OBJECTIVES: To assess the construct validity of the Short Form-12 (SF-12) in type-1 diabetes (T1D). METHODS: This analysis used data from a study investigating factors affecting setting and attainment of HbA1c targets. A total of 1,918 patients were recruited from the T1D exchange registry and completed a web-based survey;  1,846 of them finished the SF-12 section of the survey. The physical component score (PCS) and the mental component score (MCS) from SF-12 were compared between known groups. The known groups were defined by treatment intensity, duration with disease, complication, hospitalization, emergency room visits, glycemic control and working. Parametric or nonparametric tests were used depending on the scale of the measure. The Diabetes Quality of Life (DQoL) Brief Clinical Inventory is a disease specific quality of life (QoL) measure, lower score indicates better QoL. The correlations between SF-12 scores and DQoL score were also examined. RESULTS: PCS and MCS had no association with more frequent insulin injections. PCS had a positive correlation (r=-0.22, p<0.05) with duration of disease while MCS had a negative correlation (r=0.07, p<0.05). Patients with depression or anxiety had lower PCS (difference: -3.5 and -3.7, p<0.05) and MCS (- 8.4 and -6.8, p<0.05). Patients who had hospitalization due to diabetic ketoacidosis (DKA) reported significantly lower PCS (-4.0, p<0.05) and MCS (-2.7, p<0.05). More, number of emergency room visits other than for hypoglycemia or DKA was associated with lower PCS (Spearman r=-0.05, p<0.05), but not MCS. Patients with an A1c value greater than sample median had lower PCS (-2.2, p<0.05) and MCS (-3.6, p<0.05). Working patients had higher PCS (4.2, p<0.05) and MCS (1.1, p<0.05). Finally, both PCS (r=-0.38, p<0.05) and MCS (r=-0.53, p<0.05) had very strong negative correlations with DQoL score. CONCLUSIONS: This study contributed some evidence of construct validity of the SF-12 in patients with T1D.