Certain Estonian adpositions can occur either as prepositions or as postpositions (e.g. ümber maja, maja ümber ’round the house’). In this study, we refer to these as ambipositions and the goal of this study is to find the motivation for this positional variation in usage. The data come from the Estonian Dialect Corpus, which contains natural dialectal speech, allowing us to simultaneously include both linguistic as well as dialectal factors as part of the analysis. Here, we have included five ambipositions, läbi ’through’, mööda ’along’, vastu ’against’, üle ’over’ and ümber ’around’, that occurred with sufficient frequency in both positions. All utterances of these ambipositions in the corpus were included as part of this study and the results of the quantitative analysis, based on classification trees, showed that out of eight factors considered for the analyses, six influenced the realization of these ambipositions in usage, either as preposition or as postposition. The following factors significantly influenced their realization: dialect, case of the complement, word order, animacy of the complement’s referent, number, semantic function of the adposition. Verb tense and length of the adpositsional phrase were not significant for any of the analyses. In addition to identifying the abovementioned factors that influenced their realization globally, we provide an analysis for each of the ambipositions displaying their morpho-syntactic and geographical profile. In general, these profiles can be used, for example, in lexicography or in language teaching. Finally, the results indicate that the usage profiles of these ambipositions are rather specific and their realization appears to be more strongly influenced by linguistic rather than dialectal factors.