Although popular culture describes them as mortal enemies, more and more often, dogs and cats live under the same roof. Does this make them best friends? Can sharing the same social and physical environment make them similar? This study compares the approaches of dogs and cats living in the same household have towards humans and other pets as perceived by the owner. Questionnaires collected from 1270 people owning both dog(s) and cat(s) were analysed. Most dogs and cats living together are playful with familiar humans (76.2%) but dogs have a more sociable approach towards strangers and conspecifics than cats (P<0.001). Moreover, the percentage of dogs that have a playful relationship with the owner (84.0%) was higher than cats (49.2%; P<0.001). Dogs and cats living together eat in different places and show different mutual interactions: more dogs lick the cat (42.8%) and more cats ignore the dog (41.8%) than vice versa (P<0.001). However, most dogs and cats sleep at least occasionally (68.5%) and play together (62.4%; P<0.001). Although some body postures, such as the tail's position, are interpreted differently by the two species, the greater proportions of dogs and cats show a relaxed response to several kinds of approaches of their roommate. Our questionnaire confirms the common beliefs about the sociability of the dog and the privacy of the cat, but this does not result in continuous internal struggles. Most cohabitations are peaceful. Moreover, it is true that they speak different languages, but they seem to understand each other well and interpret each other's approaches in the right way. Thus, aspiring owners should not blindly believe popular assumptions, but both knowledge and respect for species-specific pet behaviours are essential to establish a balance in the household.