This paper explores the concurrent and predictive validity of the long and short forms of the Galician version of the MacArthur-Bates CDI (IDHC). Forty-two Galician-speaking children were longitudinally evaluated at age 1 ; 6, 2 ; 0 and 4 ; 0. On the first two occasions, the subjects' vocabulary and grammar skills were assessed through the IDHC. Simultaneously, lexical and grammatical measures were obtained from spontaneous speech samples. Standardized measures of general cognitive abilities (WPPSI-R) and receptive and expressive language (RDLS-III) were obtained at age 4 ; 0. Results showed high and significant levels of concurrent and short-term validity of the IDHC. Strong associations were found between lexical development at age 2 ; 0 and language scores two years later. These results coincide with those obtained with other CDI versions, and suggest that the IDHC is an effective and reliable tool.