Abstract In this paper, we discuss the restriction on the realization of non-agentive causers in nominalizations (see Adultery separated Jim and Mary. vs. ??the separation/*the separating of Jim and Mary by adultery). By comparing English to German and Romanian, we show that this restriction may have two sources: the event complexity of the nominalization or the lexical semantics of the preposition that introduces the external argument. First, the realization of non-agentive causers requires the presence of a result state component that is absent in German nominal infinitives and English ing-of gerunds. This leads to the inability of these nominalizations to host non-agentive external arguments. Second, the prepositions that introduce external arguments have a restricted distribution in Romanian and English nominalizations with the effect that the restriction appears in all Romanian nominalizations and in English derived nominals. The corresponding preposition in German is unrestricted, which explains why -ung nominals, which project a result state component, can realize non-agentive external arguments.