The present research was part of a cross-sectional project involving children aged 8 to 10 years in Porto, Portugal. The project involved a first research part at primary schools where the health tests and a questionnaire were performed and a second research part concerning environmental conditions. Two groups emerged from the health questionnaire answers: one group that reported “asthma diagnosed by a doctor” and/or “wheezing or whistling in the chest during last 12 months” and another that answered negatively to both questions. After performing the health questionnaire based on ISAAC, the children responsible were invited to participate in the environmental part of the study. The outdoor and indoor potential risk factors were extensively evaluated in children's homes. This research aimed to compare housing characteristics and indoor behaviours as environmental risk factors in the two children group and investigate whether the risks found are common. The results indicate that windows open during cleaning, standard window frame material, animals at present, dog presence, cat presence, sweep, and vacuumed floor cleaning were associated with both groups. This demonstrates that home characteristics influence some risks and may be exacerbated by certain occupants' behaviours.