This paper investigates chain properties of the comparative construction in Modern Ulster Irish (hereafter, Irish). Irish allows five patterns for A'-chains headed by an argument wh-phrase such as cad é "what," and two patterns for A'-chains headed by the reason adverbial wh-phrase cén fáth "why," when there are two COMP positions and one trace/resumptive pronoun position in the sentences. However, the comparative construction only allows two types of chains (aL, aL, t) and (aN, aL, t), and disallows all the other patterns. The generalization about chain properties of the comparative construction in Irish is thus that the chain in the construction must end with a trace. We will then discuss implications of this finding to the theory of (Irish) syntax.