Background: Although high-structured elicitation tasks have been shown to be efficient means to sample communication in children with intellectual disabilities, their validity and reliability remain to be evaluated. The aims of this study were threefold: (i) to evaluate the eliciting potential, (ii) to examine the utterance forms of proto-imperative and proto-declarative intentions, and (iii) to evaluate the reliability of two high-structured elicitation tasks. Methods: Twenty-eight children with intellectual disabilities participated in a standard assessment battery, consisting of a formal language assessment, a parent questionnaire, an elicitation task for proto-imperatives, and an elicitation task for proto-declaratives. Results: The elicitation tasks elicited significantly more proto-imperatives than proto-declaratives; with proto-imperatives being predominantly expressed with gestures and proto-declaratives predominantly with vocalizations. Furthermore, medium to large correlations were found between the elicitation tasks and the other communication and language instruments. Conclusions: Several factors need to be considered to account for the observed differences in frequency and utterance forms of the elicited proto-imperatives versus proto-declaratives. Nevertheless, the results overall suggest that the elicitation tasks for proto-imperatives and proto-declaratives can be reliably used in children with intellectual disabilities.