Abstract: It is a well-established finding that the semantic relations between the distractors and the targets have a great influence on the semantic effect during language production. The roles of situational goal and ad hoc association were explored in a picture-word interference paradigm. Results showed there were both similarity and difference between the roles of ad hoc relation and other semantic relations. Compared with unrelated distractor words, ad hoc associative distractor words slowed the latencies of picture naming and led to semantic interference effect. But the interference effect caused by ad hoc association was not stable and depended on whether there was situational goal. Ad hoc association effect was observed when the situational goal was available and disappeared when there was no situational goal. The results also showed that the ad hoc association effect appeared at the early stage of SOA. These findings were interpreted in terms of lexical cohort account, a representative model of lexical competition. Implications for nature of semantic effects in different semantic context were discussed.