Many languages encode phi-features via overt morphology, yet children's use of this morphology in comprehension tasks varies widely. Here, we use a picture-selection task to test comprehension of Spanish verbal agreement and clitics, comparing performance across and within each paradigm to examine the effect of two factors: (i) phonological salience, and (ii) semantic (under)specification. Both paradigms encode the same person and number features, but clitics may be easier to comprehend than agreement because they carry more phonological material. Within each paradigm, first- and second-person morphology may be easier to comprehend than third-person because they carry an explicit person feature. We find limited support for phonological salience and stronger support for semantic (under)specification. However, we also find evidence for a third factor affecting interpretation of third-person morphology: discourse prominence. Both adults and children permit third-person agreement and clitics to refer to the speaker and/or addressee if they have been mentioned in the immediately preceding context.