My main goal in this paper is to examine agreement in relative clauses with conjoined heads. Since there are many elements that can potentially agree with the conjoined head (i.e., the relative pronoun, the verb, nominal modifiers if present), there are many logically possible agreement patterns, only a subset of which is attested. I focus on the question of what the available (and unavailable) patterns tell us about the nature of the Agree, the mechanism responsible for agreement. The more theoretical question I examine is why sometimes Agree between a single Probe and multiple Goals surfaces as Resolved Agreement, and other times as agreement with a single Goal. Focusing on coordinate structures, I argue that Agree between a single Probe and multiple Goals in a Parallel Merge structure obligatorily leads to Single Conjunct Agreement, whereas Agree between a single Probe and multiple Goals in a non-Parallel Merge structure can result in either Single Conjunct Agreement or Resolved Agreement. This proposal has implications that go beyond Polish relative clauses, which I also discuss in the paper.