Background: Follow-up of celiac disease (CD) patients is recommended for gluten-free diet (GFD) adherence monitoring and complication detection. We recently showed that 35% of children with CD were lost to follow-up (LTFU). We aimed to characterize LTFU population, and thus identify compliance barriers to GFD and follow-up. Methods: 50 LTFU patients were investigated using a telephone questionnaire, regarding frequency of follow-up, serology testing, and adherence to GFD (using the validated Biagi score). Fifty two regular follow-up patients served as controls. Results: LTFU patients had poor adherence to GFD (average Biagi score of 2.0 ± 1.4) compared to controls (3.0 ± 1.0, p < 0.001). Only 22% of LTFU performed periodic celiac serology testing compared to 82% of controls (p < 0.001). LTFU had higher prevalence of positive celiac serology tests (50% compared to 25% of controls, p = 0.01). Fewer LTFU were National Celiac Association members (24%) compared with controls (44%, p = 0.05). Regression analysis showed positive relationships between LTFU and poor adherence to GFD (R² = 0.26737, p = 0.001), older age at diagnosis (R² = 0.30046, p = 0.03), and non-membership in a celiac association (R² = 0.18591, p = 0.0001). Conclusion: LTFU is associated with non-adherence to GFD and positive serology. Risk factors for LFTU should be identified and addressed in order to improve patient care.