Background: The difficulties experienced by intellectually able adults with autism spectrum conditions (ASCs) have been hinted at in autobiographical accounts as well as in the clinical and neuropsychological research literature. Little is known, however, about the nature of these putative difficulties, nor how people with ASCs might best be supported to make decisions for themselves. The aim of this project is to improve understanding of the effects of ASCs on decision-making in a way that may be useful to the development of guidance for those who support decision-making in adults with ASCs. Method: The project comprised two phases. The first phase was a preliminary survey of the decision-making experiences of adults with ASCs (quantitative and qualitative data). The second phase was an empirical investigation of decision-making in adults with ASCs, compared to a general population control group, which was matched for age, gender and verbal ability (quantitative data). The experimental stimuli were a battery of established and adapted neuropsychological measures, which were selected to substantiate or explore some of the findings from the preliminary survey. Results: The preliminary survey clearly showed that participants with ASCs perceive a number of difficulties in everyday decision-making. When assessed in the experimental study, the participants with ASCs reported experiencing several problems in decision-making, including avoiding decisions, more frequently than the control group. The behaviour of the ASC group on some of the laboratory tasks of decision-making were consistent with the experiences they reported. Conclusions: The findings suggest that decision-making can be particularly difficult for adults with ASCs and some possible reasons for these difficulties are identified. The findings also suggest that adults with ASCs, who are intellectually able, may benefit from support when making decisions. Specific recommendations on how to support adults with ASCs, as well as directions for future research, are discussed.