The article reflects on boundary line of ego-documents and their inherent features. The author reviews the existing notions and offers her own approach. One traditional approach identifies memoir and/or autobiographical fragments in other types of documents. Another expands the corpus of ego-documents by including sources containing memoir and/or autobiographical fragments. Adherers of the latter approach postulate that professional autobiographies, official letters, formal requests, etc. convey personal traits, providing information about their authors and their feelings and emotional state. This article proposes a compromise solution: to include such texts in the corpus of ego-documents, placing them to its periphery, if size and significance of memoir and/or autobiographical fragments is substantial; in other instances, to indicate the presence of such fragments, noting their significance for characterization of the author’s personality. The article develops a definition, according to which memoir and/or autobiographical fragment is a thematically or plot-completed textual fragment reflecting personality or memory of certain person(s), incorporated in a text that is not memoir in its origin and purpose, created at the initiative of an author and containing direct personal statements. In order to identify such fragments, the article analyzes reports of the Siberian governor-generals of the 19th century; discovers circumstances and factors, under which memoir and/or autobiographical fragments most often appear in these official documents. These are: (1) first impressions of the region; (2) highlighting issues of personal interest; (3) sharing impressions that gave rise to strong emotions. The article concludes by arguing that memoir fragments often appear in the reports of governor-generals who could be characterized as enterprising, empathic people of high intellectual level, who enjoyed the emperor's trust, but (relatively) rarely had the opportunity for personal audience. These fragments are closely related to the reports’ agenda; they reflect the personality and individuality of the authors. At the same time, fragments do not change the nature of the document, thus preventing their attribution to ego-documents. Identification of such fragments and their methodical study can expand our understanding of significance and diversity of historical sources of this type, complement and enrich information about their authors. The very idea of identifying memoir and/or autobiographical fragments in documents of different types, including official government documents, seems promising and has potential for further research.