The study aims at identifying characteristic phenotypes for children with SLI and children with sensorineural hearing impairment (HI) in language and in domains associated with language. We focus on verbal agreement inflection and phonological short-term memory, phenomena that have been repeatedly found to be impaired in both groups of children. A nonword repetition task and an elicitation task on subject-verb agreement were conducted with three groups of monolingual German children: (i) 11 children with SLI, (ii) 10 children with HI (hearing loss between 38 and 75 dB) and hearing aids, and (iii) 10 typically developing children. Data analyses reveal quantitatively and qualitatively different performance patterns with respect to verbal agreement inflection in children with SLI and children with HI but no different patterns for nonword repetition. Our results not only identify deficits in verbal agreement inflection as a sensitive, specific, and selective clinical marker for SLI in German, but they also shed some light on the nature of the deficits that underlie SLI.