This paper explores how bidirectional and unidirectional comitative constructions are processed. Bidirectional (symmetric) comitative constructions describe events where the two actors undergo the same effect described by the predicate (e.g. John was kissing with Mary), whereas unidirectional (asymmetric, instrumental-like) comitative constructions describe events in which one of the actors is the agent, and the other one is the patient (e.g. John was messing with Mary). In particular, we used the self-paced reading paradigm to determine if the two constructions access distinct mental representations. We found that the understanding of the two constructions differ as a function of word-order, and there is a difference in the processing of anaphoras referring to the Subject. Taken together, the findings suggest that mental representations activated by bidirectional and unidirectional constructions are also processed automatically during online language comprehension. Results are interpreted within the framework of the simulation paradigm (Bergen, 2007) and the situation model account (Zwaan, Radvansky, 1998).