Results of research on intentions and effects of first- and second-order argument scaffolding of computer-supported collaborative argumentation competence development and domain-specific knowledge acquisition are ambivalent. A systematic review of research in secondary and higher education (SE and HE) has been conducted to clarify and synthesise these intentions and effects, thereby differentiating between communication type (synchronous--asynchronous) and group size. Empirical research with pre-post-test designs was included only. Using specific search terms, 527 articles were found; 19 of these met pre-set selection criteria. Results indicate that HE studies intended to foster argumentation knowledge and domain-specific knowledge acquisition (i.e. knowledge construction), and reported significant effects for both types of knowledge. SE studies, however, intended to foster argumentation behaviour and domain specific knowledge acquisition (i.e. learning by doing), and showed significant effects regarding the latter only. HE studies predominantly used asynchronous, and SE studies synchronous communication. Choice of group size was not explicitly justified.