There is an ongoing discussion about the definition of mindfulness including the question whether mindfulness is a one-dimensional or multidimensional construct. Research on the Freiburg mindfulness inventory (FMI) has also reflected this debate. We have investigated the psychometric properties of the FMI-14-item in an online convenience sample of n = 244 individuals (150 female; mean age 28.7 (SD = 8.76)) with (n = 75) and without (n = 169) regular meditative training). A simplified version of the beck depression inventory (BDI-V) and the trait subscale of the state-trait-anxiety-inventory (STAI-T) were used for determining criterion validity. A one-dimensional (α = .83) and an alternative two-dimensional solution (αF1 = .77; αF2 = .69) of the FMI-14 were tested with a confirmatory factor analysis and yielded suboptimal fit indices. An exploratory analysis resulted in a reduced 8-item version of the two-dimensional solution with better fit indices, but low internal consistency (αF1 = .71; αF2 = .64). The factors could be identified as “Presence” (F1) and “Acceptance” (F2). Further investigation revealed that the substantial negative relationship between mindfulness and anxiety and depression is completely due to the “Acceptance” factor of mindfulness. This suggests that there may be heuristic value in the two-factorial solution, although for practical purposes it seems sufficient to assess mindfulness as one-dimensional construct