We present a part of broader research on word order aiming at finding factors influencing word order in Czech (i.e. in an inflectional language) and their intensity. The main aim of the paper is to test a hypothesis that obligatory adverbials (in terms of the valency) follow the non-obligatory (i.e. optional) ones in the surface word order. The determined hypothesis was tested by creating a list of features for the decision trees algorithm and by searching in data of the Prague Dependency Treebank using the search tool PML Tree Query. Apart from the valency, our experiment also evaluates importance of several other features, such as argument length and deep syntactic function. Neither of the used methods has proved the given hypothesis but according to the results, there are several other features that influence word order of contextually non-bound free modifiers of a verb in Czech, namely position of the sentence in the text, form and length of the verb modifiers (the whole subtrees), and the semantic dependency relation (functor) of the modifiers.