BACKGROUND AND AIM: According to the effect of the adhesive and substrate type on the bond strength, examination of the adhesive is required in all aspects. The aim of this study was to evaluate the shear bond strength of different adhesive systems to normal dentin (ND) and caries affected dentin (CAD) in permanent teeth. METHODS: Thirty extracted molars with small occlusal caries were selected. After preparation and determination of ND and CAD by caries detector, teeth were divided into three groups and treated with one of the two tested adhesives: Single Bond 2 (SB2), Scotchbond Universal with etch (SBU-ER), and Scotchbond Universal without etch (SBU-SE). Then composite (Filtek Z-250 XT) were attached to the surfaces and cured. After water storage (24 hours) and thermocycling (500 cycles 5-55 °C), bond strength was calculated and failure modes were determined by stereomicroscope. The data were analyzed by one-way ANOVA and post-hoc test [Tukey HSD (honest significant difference)] and with P ˂ 0.050 as the level of significance. RESULTS: Only SBU-ER had significantly higher shear bond strength than SBU-SE in ND (P = 0.027) and CAD (P = 0.046). Bond strength in SBU-ER the highest and in SBU-SE had the lowest amounts in CAD and ND. There was no significant difference in each group between ND and CAD. CONCLUSION: The 2-step etch-and-rinse adhesive (SBU-ER) had higher bond strength to ND and CAD than the self-etch adhesive (SBU-SE).