Information systems are designed, constructed, and used by people, using a set of defined processes previously deployed, as a result of software process improvement initiative. Software process improvement is not a purely technical task, but a complex psycho-socio-technical process. This paper presents a systematic review to identify the categories most used in literature to classify software process improvement success factors and the critical success factors related to people. We found several studies related to critical success factors, but only 10 of them proposed a critical success factors classification. The quantitative data from a systematic review were analyzed using descriptive statistics. As a result the following common categories are identified: organization, people and process. The critical success factors related to people are presented in this paper. © Springer-Verlag Berlin Heidelberg 2013.