In individuals with Down syndrome (DS) deficits in verbal short-term memory (VSTM) and deficits in sentence comprehension co-occur, suggesting that deficits in VSTM might be causal for the deficits in sentence comprehension. The present study aims to explore the presumed relationship between VSTM and sentence comprehension in individuals with DS by specifically targeting the influence of task demands. The authors assessed VSTM skills in 18 German-speaking children/adolescents with DS by a nonword repetition (NWR) test and elicited data from three different tasks on the comprehension of complex sentence structures: two sentence-picture-matching tasks (TROG-D and a passive test) and one picture-pointing task on object "wh-"questions. Whereas performance in NWR yielded a significant degree of prediction for scores obtained in the TROG-D and in passive comprehension, no significant degree of prediction was found for NWR and object "wh-"question comprehension. Moreover, implicational scaling analyses indicated that mental-age adequate performance in sentence comprehension did not imply adequate performance in NWR. Research is needed that specifies the relation between memory systems and sentence comprehension while considering the influence of task demands.