This study investigated the difference in clinical characteristics of fallopian canal dehiscence associated with pars flaccida and pars tensa cholesteatomas for the purpose of increasing the preoperative detectability of dehiscence. A total of 189 ears of patients 7–80 years of age (mean 42 years) with pars flaccida cholesteatoma and 63 ears of patients 9–84 years of age (mean 50 years) with pars tensa cholesteatoma were studied. All patients had undergone prior surgical management at our institution from January 2006 to April 2012. The incidence of fallopian canal dehiscence and its location were compared between pars flaccida and pars tensa cholesteatomas. Intraoperative findings of coexistent pathologies, including destruction of the stapes superstructure, labyrinthine fistula, and dural exposure, were compared between the dehiscence and no-dehiscence groups for the two types of cholesteatomas. The incidence of dehiscence was significantly higher in patients with pars tensa cholesteatoma (55.6 %) than in patients with pars flaccida cholesteatoma (26.5 %). Dehiscence located posterior to the cochleariform process occurred slightly more frequently in patients with pars tensa cholesteatoma than in those with pars flaccida cholesteatoma. In patients with pars flaccida cholesteatoma, labyrinthine fistulas and dural exposure were significantly more frequent in the dehiscence group than in the no-dehiscence group. Fallopian canal dehiscence is more frequent in patients with pars tensa cholesteatoma than in those with pars flaccida cholesteatoma. Especially in patients with pars flaccida cholesteatoma, paying special attention to these coexisting pathologies is important to increase preoperative detectability of dehiscence.