This paper reports results on presumably the first city-wide mobile participation trial (Living Lab) examining citizen participation in urban planning, conducted in Turku, Finland, in 2015. The questions examined are the socio-economic characteristics of the application users, as well as their motivations to participate. The inclusion of online participation has been discussed widely in literature on e-participation and the digital divide, arguing for a great influence of socio-economic factors, interest in the topic, and users’ online skills. The results reveal that this application, too, was used predominantly by young adults and middle-aged, highly educated, and technology savvy citizens, who were already interested in urban planning. Their use of the application was motivated primarily by the opportunity to bring their own ideas and issues to the city authorities’ attention, rather than participating in missions given by the municipality or discussing planning issues with fellow citizens, indicating a rather individualistic usage interest. The location-based features and ease of use of a mobile application were valued highly. Those who idled reported predominantly technical challenges with the app.