In software engineering (SE) and in the computing disciplines, papers presented at conferences are considered as formal papers and counted when evaluating research productivity of academic staff. In spite of this, conference papers may still be extended for publication in academic journals. In this research, we have studied the process of extension from conference to journal publication, and tried to explain the different purposes these two forms of publication serve in the field. Twenty-two editors in chief and associate editors in chief of major publications in SE and related fields were interviewed, and 122 authors of extended versions of conference papers answered a Web questionnaire regarding the extension of their papers. As a result, the process of extending conference papers for journal publication in SE is recorded. In the conclusion, we comment on the following: (a) the role of the conference in the development of the research work; (b) the review process at the conference and at the journal stage; and (c) the different purposes conference and journal publication fulfill in SE.