Background and Purpose: The comprehensive Developmental Inventory for Infants and Toddlers (CDIIT) is a new developmental test designed in Taiwan and lacks concurrent validity information. This study investigated the concurrent validity of the CDIIT with the Bayley Scales of Infant Development-Ⅱ (BSID-Ⅱ) in preterm infants aged 6-18 and 21-40 months, respectively. Methods: We recruited 160 preterm infants (84 boys, 76 girls) with a corrected age of 6-18 months and followed them up until 21-40 months of age. One tester administered the CDIIT and BSID-Ⅱ to all infants. Developmental ages (DAs) and developmental quotients (DQs) from both tests were analyzed with Pearson correlation and κ tests. Results: Correlation coefficients for DAs and DQs between the 2 cognitive and motor subtests and classification agreements were high at 6-18 months (r=0.80-0.97; κ=0.80, 0.85) and moderate to high at 21-40 months (r=0.60-0.77; κ=0.44, 0.57). DQ classification for the CDIIT motor subtests tended to be higher than for the BSID-Ⅱ motor scales at 21-40 months. Conclusions: In preterm infants, concurrent validity between the motor and cognitive subtests of the CDIIT and the BSID-Ⅱ was acceptable. The CDIIT can be thus used in clinics for the early identification of developmental delay in infants and toddlers.