This paper explores modals in Croatian and Slovenian languages. The main goal is to detect whether there are analogous modal verbs in both languages that have undergone a certain degree of grammaticalization. The paper starts with an attempt to define the concept of modality with emphasis on modal verbs and their place in different perspectives of modality theory. The following is a short overview of modal verbs descriptions in Croatian and Slovenian normative literature with the purpose of detecting differences in modal verbs categorizations. This leads to contrastive analysis of Croatian and Slovenian modals based on selected examples from web corpuses, which enables us to draw insights about similarities and differences in modal systems of both languages. In the end, the account and interpretation of conducted psycholinguistic research of modal verbs morati and trebati in Croatian language is given. Research was conducted through a paper survey on 42 Croatian language speakers with the purpose of exploring differences in imageability of modal verbs morati and trebati in different contexts.