Relational reasoning develops slowly. Children's difficulty may stem from the difficulty of inhibiting object attention, but the role of object attention in relational reasoning remains unclear. Experiment 1 tested the hypothesized trade-off between processing relational and object information using a novel match-then-recognize paradigm. The relational-mapping task required participants to match ordinal positions of objects, followed by an object memory test. In adults, there was a clear trade-off: object recognition was negatively correlated with relational mapping. Children's object recognition was lower than adults' but positively correlated with relational matching. Experiment 2 further tested the role of inhibition by occluding object matches. Surprisingly, older children and adults actively removed occluders, to their own detriment, whereas the youngest children neither removed occluders nor were helped by them. Findings suggest that selective attention can be crucial for relational reasoning, but ignoring object information may be less important for success than total allocated attention.