Abstract. In this paper, we compare the use and functions of definite and indefinite article-like determiners in Estonian and Finnish. Our main aim is to explore whether the factors that explain the choice of particular determiner forms are similar in Estonian and Finnish. We use a picture-sequence based elicitation experiment to collect spoken narratives from adult native speakers of Estonian and Finnish, and apply non-parametric tree and forest models to analyze the data. Our findings indicate that number of mention and animacy are important predictor variables in both languages, but their exact effect is divergent. We also find that in Finnish, case of the determiner NP proves to be an important factor, while in Estonian, syntactic role of the NP explains some aspects of determiner form choice. Nevertheless, the overall usage frequency of determiners is modest in the Estonian and Finnish data, and the process of grammaticalizing articles is only in initial stages in both languages.