OBJECTIVE: Celiac disease (CD) is a common comorbidity of type 1 diabetes (T1D). Long-term consequences of CD are not completely understood, and adhering to a gluten-free diet is a burden for many patients. We investigated the effect of CD on vascular risk factors in a large cohort of T1D patients aged <20 yr. RESEARCH DESIGN AND METHODS: Within the longitudinal Diabetes Patienten Verlaufsdokumentation (DPV)-diabetes registry, data were analyzed from 59 909 < 20-yr-old T1D patients treated at 392 centers in Germany and Austria. A total of 974 patients with biopsy-proven celiac disease (BPCD) were compared with 28 398 patients without CD with respect to blood pressure (BP), lipids, glycohemoglobin (HbA1c ), body mass index (BMI), and reported smoking behavior. RESULTS: Patients with T1D and BPCD showed significantly lower high-density lipoprotein (HDL) cholesterol levels [median (interquartile range): 53.0 (43.0-62.6) mg/dL] than patients without CD [55.0 (45.0-66.0) mg/dL; p < 0.01; p < 0.001 after adjustment for confounding variables]. Systolic BP was lower in patients with CD [105.5 (100.0-112.5) mmHg] than in patients without CD [110.0 (102.0-117.0) mmHg; p < 0.0001; p < 0.001 after adjustment]. There were no significant differences regarding smoking behavior, BMI, or HbA1c . In a subgroup of 335 patients with BPCD, HDL cholesterol was measured 1 yr after diagnosis of CD:HDL increased by 8% (p < 0.01). CONCLUSION: Young people with T1D and CD have lower HDL cholesterol values than patients without CD. As low HDL cholesterol is associated with vascular risk, our findings support screening for CD and monitoring of HDL cholesterol in young people with T1D.