Theory of mind (ToM) refers to the capacity to attribute certain independent mental states, contents and processes to others - such as desires, concepts, intentions, beliefs and emotions (Wimmer & Perner, 1983). As there is a body of research with respect to the development of ToM in children, much less is known about adult mentalizing abilities, especially regarding the relationship between cognitive functioning and ToM. The present study aims to investigate a new instrument, called ToM-Stories and its relationship to the established ToM-Picture-Test (Bruene et al. 2005) and to cognitive functioning by using the Trail Making Test. Our ToM-Stories consist of brief stories, each describing a real life situation of various degree of complexity. All of them involve unintended misleadings in the sense of a false belief. Their comprehension requires mindreading at different levels of intentionality. The sample was composed of 79 adults, 45 (57%) women and 34 (43%) men, ranging in age from 18 to 88. Reliability analyses of the ToM-Stories yielded a Cronbach’s alpha of 0.79 (false belief-first order), 0.74 (false belief-second order), and 0.65 (false belief-third order). Correlation analyses showed moderate values between ToM-Stories and the Tom-Picture-Test (r = 0.496; p ≤ 0.0001) as well as the Trail Making Test B-A (r = −0.481; p ≤ 0.0001). The findings of the current study provide evidence that cognitive flexibility is an important competence in promoting representational understanding of the mind.