The objective of this study was to compare the effectiveness of premaxilla molding between acrylic obturator and polyvinyl obturator in treating infants with complete unilateral cleft lip and palate. The subjects comprised 36 infants with complete unilateral cleft lip and palate (age ranged from 1 to 26 days; mean age 6.5 days). The subjects were divided into 2 groups as follows: 20 in the control group and 16 in the experimental group. Acrylic obturators were used in the control group, while the polyvinyl obturators were used in the experimental group. The subjects were treated by the similar standard protocol until the requirements for lip surgery were accomplished at the age of 3 - 4 months. Arch width, arch height and cleft size were measured from the study casts and compared with Analysis of covariance. The results showed that there was no statistically significant difference between two types of obturator. Arch ratios at pre and post treatment were calculated and compared with t-test for equivalence study by equivalence margin 0.1. There was significant equivalence at 95% confidence interval in arch ratio between the two groups (p < 0.001). It was shown that the polyvinyl obturator could be equally effective for premaxillary molding in complete unilateral cleft lip and palate infants as well as the acrylic obturator.