The study explores the criterion-related validity of the Swedish version of the Communicative Development Inventories–Word & Sentences (SECDI-W&S). In two follow-up procedures, SECDI-W&S was used to assess vocabulary and grammar skills in 32 children at ages 1;10 or 2;4. At the first follow-up, 14 months later (at ages 3;0 or 3;6), two grammar tasks from the SECDI-W&S and one narrative task (frog story) were given to 27 children. Predictive validity ranged from .50 to .60 for most assessed skills over the 14-month period, whereas concurrent validity scores at ages 3;0 or 3;6 ranged from .48 to .70. The second follow-up at 26 months (at ages 4;0 or 4;6) was conducted with the narrative task only. Predictive validity from ages 1;10 or 2;4 for the second follow-up remained high for some of the measures; however, for other measures it diminished, which could be partly accounted for by ceiling effects. The overall results confirm that the criterion-related validity of the SECDI is sound.