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Introduction Recently it was shown that antibodies recognizing partially deamidated gliadin have higher sensitivity and specificity for celiac disease (CD) in comparison to antibodies recognizing native gliadin. The aim of the study was to assess the diagnostic performance of new ELISA test in which the antigen represents a repetitive motive of deamidated gliadin peptides (GAF-3X) and to compare it with anti-tTG test. Materials and methods Study included 56 pediatric patients (F/M=37/19 ; median age 11 years (range 7-15), for whom CD serology was requested. Anti-GAF-3X IgA and IgG together with anti-tTG IgA antibodies were measured in all sera using ELISA assays (Euroimmun, Lübeck, Germany). Manufacturer proposed cut off values were 20 RU/mL for anti- tTG and 25 RU/ml for GAF-3X IgA and IgG. Results Out of 56 patients 8 were positive for all 3 autoantibodies type, 1 for GAF-3X IgA and anti- tTG, 13 for anti-tTG and 1 for anti-GAF-3X IgA only. CD was biopsy confirmed in 14 patients of whom 7 were positive for all 3 autoantibodies type, 1 for anti-tTG and GAF-3X IgA and 2 for anti-tTG only. The residual 4 CD confirmed patients were on gluten free diet and 3 of them were seronegative while anti-tTG was positive in one. With cut off values proposed by the manufacturer sensitivity and specificity was 100% and 73, 8% for anti-tTG, 80, 0% and 95, 2% for anti-GAF-3X IgA and 70.0% and 97.6% for anti-GAF- 3X IgG. According to ROC analysis, sensitivity and specificity for anti-tTG IgA was 100% and 95.2%, for anti-GAF-3X IgA 90.0% and 92.9%, and for anti-GAF-3X IgG 70.0% and 97.6% RU/mL, respectively. Optimal cut-off value for tTG-IgA was 48.6 RU/mL, and 22 RU/mL for both anti-GAF-3X IgA and anti-GAF-3X IgG. The correlation between anti-tTG IgA and GAF-3X IgA or GAF-3X IgG was weak, but statistically significant (Spearman rho for GAF-3X IgA=0.555, for GAF-3X IgG = 0.606, P