It is commonly believed that telling a lie is more difficult than telling the truth. However, the precise reason for this difficulty remains uncertain. The Activation-Decision-Construction Model (ADCM; Walczyk, Roper, Seemann & Humphrey, 2003) suggests that telling a lie will take longer than telling the truth due to the additional processes involved, such as suppression of the truth. Experimental work investigated the lie construction component of the model by manipulating the number of plausible lie responses available. Participants lied and told the truth regarding the colour of a square presented on a computer screen. Results support the general claims of the ADCM, but suggest that longer response times when individuals lie to questions with more than one possible lie response relate to a fixed cost choice between multiple response possibilities. This contributes to current understanding of which situations may enhance processing differences between telling a lie and telling the truth.