Some unaccusative verbs in Italian have the complement sentence as an argument which becomes the logical subject of the verb. We can describe the syntactic structure as the complement sentence (CP), which functions as a logical subject of the sentence, and a selective dative (a NP), as in (1).
(1) [V V]([PP a NP])[CP CP]
There is the finite complement sentence, introduced by the complementiser che, and two non-finite complement sentences: zero infinitive (φInf) and di infinitive (diInf).

In this paper, we analyze the distribution of the complement sentences in Italian unaccusative verbs by utilizing the CODIS Corpus; and examine the forms of each verb from the point of view of their syntactic structure. The relation between the syntactic structures of unaccusative verbs and the argument structure can be described as in (2):
(2) a. <(Experiencer), Proposition>
the Small Clause Structure：
A② [VP [V’ [V V]([PP a NP])[SC [CP che][AP AP]]]]
A③’ [VP [V V][SC [DP DP][DP φInf]]]
A④ [VP [V’ [V V]([PP a NP])[SC [DP φInf][AP AP]]]]
the Unaccusative Structure：
A①’ [VP [V’ [V V]([PP a NP])[CP che]]]
A⑤’ [VP [V’ [V V][PP a NPi][CP [C di][TP [PRN PROi][T’ [T ][VP Inf]]]]]]
b. <(Experiencer), Theme>
the Unaccusative Structure：
B① [VP [V’ [V V]([PP a NP])[CP che]]]
B② [VP [V’ [V V]([PP a NP])[CP φInf]]]
B④ [VP [V’ [V V][PP a NPi][CP [C di][TP [PRN PROi][T’ [T ][VP Inf]]]]]]
c. <Benefactive, Theme>
the Small Clause Structure：
B③ [VP [V V][SC [DP φInf][PP a NP]]]
d. <(Benefactive), Event>
the Small Clause Structure：
B⑤ [VP [V’ [V V]([PP a NP])[SC [PRN proi][CP [C di]
[TP [PRN PROi][T’ [T ][VP Inf]]]]]]]
Although in modern Italian the finite complement sentence and φInf complement sentence that originally existed coexist with the diInf complement sentence that developed from the finite complement sentence, the distribution is dependent on the syntactic structure.

本稿は、2015年9月5日、広島大学国際協力研究科で開催された第45回西日本言語学会において「イタリア語非対格自動詞の動詞補文における使用分布と統語構造」と題して口頭発表を行ったものに加筆・修正を施したものである。