In this case study, we examined the influence of five groups of communication activities on the quality of student's contributions to online discussion. The activities were the nominal group technique, debate, invited expert, WebQuest and reflective deliberation. Quality of discussion was operationalised as "cognitive presence", a construct developed to investigate the role of critical discourse in higher, distance education contexts. Using the quantitative content analysis technique, the postings of 19 students in an undergraduate university course were assigned to one of the four categories of cognitive presence. Across the five activities, the proportion and number of contributions categorised in the highest phases of cognitive presence was low (20.21%), but was highest during the Webquest and debate activities. There are three advantageous qualities of these two activities, we argue: (1) They were well structured; (2) They provided clearly defined roles and responsibilities for the students; and (3) They provoked the students to explicitly confront others opinions.