Previous research shows that synchronous text discussion through group support systems (GSS) can improve the exchange of information within teams, but this improved information exchange usually does not improve decisions because participants fail to process the new information they receive. This study examined one potential cause for this failure: Dual-task interference caused by the need to concurrently process new information from others while also contributing one's own information to the discussion. Although prior research argues that dual-task interference should be minimal, we found that it significantly reduced participants' information processing and led to lower decision quality. The effect sizes were large, suggesting that dual-task interference is one of a handful of major factors that exert the greatest influence on information processing and decision-making performance. We believe that these results call for an increased emphasis on and understanding of the cognitive underpinnings of GSS and virtual team decision making.