Abstract Background Patient reporting of symptoms in a questionnaire with a 7-day recall period is expected to differ from reporting in daily symptom diaries. Methods 38 patients with cystic fibrosis (CF) completed 77 week-long symptom diaries. Each diary day comprised 13 symptom items with 5-point response scales. Days 1–6 of the diary had a 24-hour recall period. Day 7 had a 7-day recall period. Concordance of 7-day recall with summary descriptors of daily reports (e.g. mean, maximum) was examined and ability of 7-day recall and mean of daily reports to discriminate between well and ill periods of health compared. Results The average difference in scores was less than 0.25 response scale points. 7-day recall was most concordant with the mean of daily reports. Discriminant ability was comparable. Conclusions In this study sample, a questionnaire with 7-day recall provided information similar to a daily diary about the week-long experience of CF symptoms.