In an ultimatum game, participants were randomly assigned to the role of allocator or recipient and to interact face-to-face (FtF) or over computer text chat (computer-mediated communication [CMC]). The allocator was given money to divide. The recipient was unaware of the amount given, so the allocator could deceive the recipient. Perception of the allocator having a dishonest demeanor increased recipient suspicion of deception, but reduced detection accuracy for truths. Demeanor cues did not help detect deception. Recipients were better at detecting lies CMC than FtF. Overall, truth bias did not differ between CMC and FtF. Rates of deception did not differ between CMC and FtF, but type of deception marginally differed. There was more deceptive omission used in FtF and more deceptive commission (bald-faced lies) used in CMC. Results are discussed in terms of demeanor and truth bias.