The evaluation of quality of life (QoL) plays an increasingly important role in clinical research and drug trials in ALS. However, most of the scales employed so far are based on a fixed external value system, and may therefore not reflect the patients' subjective perception of QoL accurately. In addition, many ALS patients complain about the psychological distress inflicted by QoL questionnaires which focus on functional status, as they constantly remind patients of their deterioration. We therefore asked 42 ALS patients to assess, using visual analogue scales, their subjective perception of the validity of three QoL instruments as well as the emotional distress caused by them. The scales were: the Sickness Impact Profile (SIP), the Short Form 36 (SF-36), and the Schedule for the Evaluation of Individual QoL-Direct Weighting (SEIQoL-DW). Patients were examined at least three times at two-month intervals. The SIP was filled out by all patients, the SF-36 and the SEIQoL-DW were assigned at random. The validity of the SEIQoL-DW was rated higher than that of the SIP (p<0.001) and of the SF-36 (p<0.001). The SIP imparted a higher emotional distress to patients than the SEIQoL-DW (p<0.005), with a trend in the same direction for the SF-36 (p=0.082). The most frequently mentioned QoL-relevant domains in the SEIQoL-DW were family (100%), health (53%), and profession (50%). These results should prompt further discussion and investigation on the most appropriate way to assess QoL in patients with ALS.