The present study examined the relationship between temperament traits and the rate of discounting of delayed and probabilistic losses. It was found that the rate at which delayed losses were discounted was related to sensation seeking and impulsivity (groups of high sensation seekers and high impulsive subjects discounted at a higher rate than groups with the opposite temperamental characteristics), but not to extraversion. The rate at which probabilistic losses were discounted did not differ between high and low sensation seeking participants, nor between introverts and extroverts. However, high impulsive participants showed lower probabilistic discounting rates than low impulsive individuals. The study revealed an important inconsistency between the way impulsivity is defined in behavioural psychology and in the psychology of individual differences.