This study compared results from Internet and written questionnaires about respiratory symptoms in order to find out if both forms of the survey yielded the same answers. One thousand seventy-one students, ages 13 to 17, were asked to complete either an Internet or a written questionnaire. The demographic characteristics of the participants equalled those of the general Dutch adolescent population. Participants were randomly assigned to fill out an electronic or written questionnaire. In addition to eight items from the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, two items on doctor visits (medical attention) regarding asthma or allergic disease during the past 12 months were included. The participation rate was 87%. The Internet version of the questionnaire showed fewer missing answers than the written version, but this was not statistically significant. The respiratory items did not show statistically significant score differences between the Internet and written modes of administration, and there was no visible trend for higher respectively lower scores by either mode of questionnaire administration. From these results, we conclude that respiratory questionnaires may be provided to adolescents electronically rather than on paper, since both approaches yielded equal results. To generalize these findings, we recommend repeated studies in other settings.