The paper focuses on Slovenian comitative constructions with two human participants who are involved in the same situation: the first participant, most frequently expressed by a nominative noun phrase, acts as a nucleus of the comitative construction, whereas the other accompanying participant is expressed by means of a prepositional phrase. All Slovenian examples of comitative constructions are presented in parallel with their possible equivalents in Russian and Shtokavian.  Comitative constructions typically found in Slovenian are those that act as subjects, the subject emphasizing the predicative relation. The predicative relation suggests mutual dependence of participants and predicates, which is why the choice of the form of the predicate often determines the number of referential participants.  The first part presents two comitative constructions. The first one includes two participants, which are often detached, and a singular predicate (Slovenian Anton je gledal film z Ano ‘Anton watched a movie with Ana’). The second one consists of two contiguous participants that act as a complete noun phrase (Slovenian Midva z Ano gledava film ‘Ana and I are watching a movie’) demanding a non-singular predicate. Differences between Slavic languages show up in the second comitative construction: Slovenian, for example, only allows constructions with personal pronouns in dual (midva z Ano), in which the pronoun has to include the other participant in the instrumental case. This is how Slovenian differs from Shtokavian, in which contiguous constructions with an inclusive accompanying participant and a plural predicate are not possible (*mi s tobom pišemo).  The inclusiveness of participants in Slovenian comitative constructions is also related to the dual form of the predicate, especially in those cases in which the first participant remains unexpressed (Z Ano piševa pismo ‘Ana and I are writing a letter’). The dual form of the predicate is linked to the difference between Slovenian and Shtokavian, which lacks dual. The unexpressed pronoun vidva (‘you two’) denoting the addressee in the Slovenian sentence S profesorjem se lepo imejta / Lepo se imejta s profesorjem (‘You and professor have a nice time’) may receive an inclusive interpretation that includes the accompanying participant. In its Shtokavian counterpart with a plural predicate L(ij)epo se provedite s profesorom (‘Have a nice time with the professor’), however, the unexpressed pronoun vi (‘you’), is by no means in an inclusive relation to the professor. Profesor in the Shtokavian example assumes the role of the circumstance and is thus not part of the comitative construction. The comparison with Shtokavian shows that it is precisely the Slovenian dual (the dual form of the predicate with a dual personal pronoun) that enables and also announces the inclusive comitative construction.  It should be emphasized that contiguous comitative constructions with the first participant expressed by a proper noun and a non-singular predicate (Russian Павел с Евой пришли ‘Pavel and Eva came’) are not characteristic of South Slavic languages. In these languages, a union of two proper noun agents is expressed through coordination and conjunction (Slovenian Pavel in Eva sta prišla, Shtokavian Pavel i Eva su došli). In contrast to Russian, the use of inclusive contiguous comitative construction in Slovenian and Shtokavian is rather unusual.  The second part discusses differences between predicates that necessarily imply a common action and predicates that can only express a common action contextually. It was established that reciprocity in the first type of predicates is more frequently expressed with reflexive verbs in Slovenian and Shtokavian than in Russian (Slovenian prepirati se, Shtokavian svađati se vs. Russian спортить ‘argue’).  It is also noteworthy that Russian fundamentally differs from South Slavic languages in that a comitative construction is also used to express common possession (Russian твоя/ваша с Машей книга ‘your and Masha’s book’). Different possibilities of translating this possessive construction into Slovenian are provided.