Preventive resin restorations is a restorative technique in which carious enamel is cut and bonded to resin composites while some areas of intact enamel are bonded to sealant. Objective: to evaluate microtensile bond strengths of three adhesive systems to unground and ground enamel of primary teeth. Methods: 47 caries-free primary molars were sectioned mesio-distally into 94 buccal and lingual halves. 64 specimens were divided into 4 groups (n = 16) for bond test of unground enamel. After cleaning with pumice, the occlusal surface of each specimen was conditioned with the following adhesive systems: Gr I- primer of Clearfil SE Bond (CSP), Gr II-Clearfil SE Bond (CS), Gr III-Adper Prompt (AP) and Gr IV- 35 % phosphoric acid (CT), and resin sealant was built up and light cured. The other 30 specimens were used for ground enamel. Buccal/lingual surfaces were polished with 600 grit SiC papers. All specimens were divided into 3 groups (n = 10) and bonded to these adhesives: Gr I-CS, Gr II-AP and Gr III-Single Bond (SB). Hybrid resin composites were built up and light cured. After 24-hour water storage, all specimens were prepared for microtensile bond strength test. Bond strengths were compared using ANOVA and LSD with the significance level of 0.05. Results: in unground occlusal enamel, bond strengths of CSP, CS, AP and CT were 15.7 (7.5), 15.4 (6.5), 18.3 (6.9) and 16.5 (7.4) MPa, respectively. There was no statistically significant difference among four groups (p>0.05). Bond strengths of three adhesive systems to ground enamel also showed no significant difference (p>0.05). Bond strengths of CS, AP and SB were 41.5 (10.5), 38.8 (8.8) and 39.5 (8.9) MPa, respectively. Conclusions: adhesion of self-etching adhesive systems to primary tooth enamel is as effective as that of total-etching system regarding to surface preparation.