This paper analyses the use of various communication channels in science teachers' professional development project aiming to develop versatile uses for ICT (Information and Communication Technologies) in science teaching. A teacher network was created specifically for this project, and the researchers facilitated three forms of communication concentrating on the topic of ICT in science teaching. The three forms of communication were face-to-face interaction, mediated interaction, and mediated quasi-interaction. Based on case study data and participating teachers' self evaluation, during the course of the project, the use of ICT in science teaching increased. As predicted, face-to-face communication appeared to be felt more effective than mediated interaction or mediated quasi-interaction. However, informal discussions in small groups turned out to be more important than expected. The results suggest that the design of future professional-development projects should make room for more informal communication. (Contains 6 tables.)