A key component of decision aids (DAs) are the Value Clarification Exercises (VCEs), however, rates of completion VCEs are variable. The aim of this paper is to propose explanations for these variations.A review of the rates of completion and the reasons provided across eleven studies evaluating five different DAs was conducted.Retrospective evaluation does not appear to be an indication of prospective use. Differences in mode of administration are unclear. Gender does not appear to have a difference on completion rates. Complexity of the decision appears to reflect rates of VCE completion. The main reason provided for non-completion of VCEs was that patients had already made a decision.VCEs have shown a trend to producing better congruence between values and choices, but it remains unclear how VCEs impact on the quality of the decision. Value of VCEs in treatment decision-making has not been previously established and our data indicate information alone might be enough to clarify concepts.DAs are becoming more widely used in practice. It is important to understand the elements in a treatment decision-making so that the burden on the patient is at a minimum in practice.