Eye contact is believed to be an important factor in normal human communication and as a result of this a head mounted display (HMD) is often seen as something intrusive and limiting. This can be especially problematic when AR is used in a collaborative setting. The study presented in this paper aims to investigate the effects an HMD-based AR system can have on eye contact behaviour between participants in a collaborative task and thus, in extension, the effects of the HMD on collaboration itself. The focus of the study is on task-oriented collaboration between professionals. The participants worked through three different scenarios alternating between HMDs and regular paper maps with the purpose of managing the crisis response to a simulated major forest fire. Correlations between eye contact between participants and questionnaire items concerning team-and taskwork were analysed, indicating that, for the paper map condition, a high amount of eye contact is associated with low confidence and trust in the artefacts used (i.e. paper map and symbols). The amount of eye-contact in both conditions was very low. It was significantly higher for conditions without HMDs. However, the confidence and trust in the artefacts was generally rated significantly higher with HMDs than without. In conclusion, the decrease in eye contact with HMDs does not seem to have a direct effect on the collaboration in a professional, task-oriented context. This is contrary to popular assumptions and the results are relevant for future design choices for AR systems using HMDs.