In this paper, we investigate topicalization patterns of German particle verbs by comparing the syntactic behavior of semantically transparent and non-transparent particle verb constructions. We propose a classification that allows us to cover the whole transparency spectrum and to distinguish between fully transparent and fully non-transparent particle verbs. Given this classification, we report on a questionnaire study that provides empirical evidence for the claim that information structural constraints in combination with the degree of semantic transparency govern topicalization patterns in particle verb configurations. We conclude by pointing out potential additional constraints on topicalization in particle verb constructions that go beyond information structure.