Objectives: The aim of the present study was to evaluate the influence of different bonding area sizes on tensile bond strength of two different dentin adhesives (Excite, Clearfil New Bond) in vitro. Methods: Eighty freshly extracted third molars were included. All teeth were specially prepared obtaining dentin specimens with a total thickness of 3.5 mm under standardized conditions. The specimens were randomly assigned to eight experimental groups of ten samples each: Group C1: Clearfil (diameter 1 mm), group C2: Clearfil (2 mm), group C3: Clearfil (3 mm), group C4: Clearfil (4 mm); group E1: Excite (1 mm), group E2: Excite (2 mm), group C3: Excite (3 mm), group C4: Excite (4 mm). Tensile bond strength of the above mentioned adhesive agents was measured 15 minutes after application and light curing of the composite material (Tetric Ceram, colour A2) using an universal testing machine. Results: Following tensile bond strengths were evaluated (mean value and standard deviation in MPa): group C1 18.5 (± 10.4), group C2 9.97 (± 3.76), group C3 4.78 (± 2.21) group C4 4.68 (± 2.41), group E1 10.84 (± 6.62), group E2 7.22 (± 3.11), group E3 4.87 (± 1.90) and group E4 3.56 (± 1.11). Statistical analysis showed a significant influence of the used dentin bonding agent and the bonding area size on tensile bond strength (p Conclusions: It can be concluded that different sizes of bonding areas have an influence on tensile bond strength of both dentin adhesive systems tested. The higher bond strength observed in smaller bonding area sizes might explain the known differences between in vitro test and clinical performance of dentin adhesives. Keywords: dentin, dentin bonding agent, tensile bond strength