INTRODUCTION: Metastasis and invasiveness of thyroid carcinoma might be correlated with over-expression of genes which encode proteins responsible for cellular adhesion. The aim of our study was to compare by means of real-time Q-PCR expression levels of chosen genes in papillary thyroid carcinoma (PTC) with respect to normal thyroid tissues. MATERIAL AND METHODS: Total RNA was isolated from 38 paired normal and PTC samples. 0.5 mug of RNA was used in the reverse transcription reaction. cDNA was further used in Q-PCR reaction. As endogenous control we used GUS gene, as its expression was stable in all analysed samples. RESULTS: The analyzed genes were found by microarray studies as characteristic in differentiated papillary carcinoma and normal tissue. The levels of gene expression, estimated by quantitative analysis of particular transcripts were increased in papillary thyroid carcinoma with the following average values: 0.76 for MMP11; 1.08 for CLDN1; 3.98 for LRP4; 4.57 for FLRT3; 26.6 for MRC2; 2.76 for NRCAM; and 1.35 for EVA1 (arbitrary units), whereas in normal thyroid tissues treated as control the respective values were: 0.09; 0.145; 0.7; 0.74; 7.9; 0.85 and 0.396 units. To confirm the overexpression of mentioned genes the conservative Kolmogorov-Smirnov test was used. Differences in expression between normal thyroid tissue and PTC were statistically significant. CONCLUSIONS: Among the analyzed genes two show the largest difference in expression between papillary thyroid cancer and normal tissue: MMP11 (metalloproteinase 11) and CLDN1 (claudin 1). The MMP11 gene can be characteristic for various malignant thyroid carcinomas, because its increased levels are present also in medullary thyroid carcinomas. It appears that claudin 1 may be used as a marker of PTC, however a verification on independent collection of tumors of this result is required.