Abstract : Teenagers write today in multiple formats, whether paper or digital. Their uses are not known precisely. An ethnographic investigation leads us to observe and meet with teens for two years in order to clarify their uses. Writing is approached here in terms of geography and information science in order to clarify its place in their life. This thesis tries to understand what role the writing plays in the identity process of adolescents in all the technical, social and spatial layouts and devices in which they are enrolled. The methodological and epistemological support is based on the notion of situation and the case thinking. Both detailed descriptions of writing situations and portraits of adolescents afford to identify their uses in most of their activities. With the survey results, we invite to reconsider the study of literacy and to pave the road for a geography of writing.