Introduction: Apart from classical symptoms such as rhinorrhea and nasal itching, patients with seasonal allergic rhinitis often complain about an impairment in their sense of smell and a reduction in their quality of life. Aim of the present study was to investigate the effects of a topical nasal steroid (mometasone furoat nasal spray) on olfactory function and quality of life in patients suffering from seasonal allergic rhinitis. Materials and methods: Twenty-four patients were enrolled in this randomized, double-blind, placebo-controlled study. Symptoms of allergic rhinitis were evaluated with questionnaires before and 2 weeks after treatment with mometasone furoate nasal spray. The Rhinitis Quality of Life Questionnaire was used for the assessment of quality of life. Olfactory function was quantified using the "Sniffin' Sticks" test. Nasal airflow was measured with anterior rhinomanometry. Results: Symptoms of allergic rhinitis were reduced in all patients; improvement was found to be more pronounced in the mometasone group. Significant differences between treatment groups were detected for the quality of life parameters "practical problems" and "nasal symptoms". Olfactory function decreased in the placebo group while it improved in the mometasone group. Significant differences between groups were found with respect to odor threshold. Changes of the olfactory function did not correlate with changes in nasal airflow. Discussion: Treatment of allergic rhinitis with mometasone nasal spray not only leads to an improvement of classical symptoms but also increases quality of life and olfactory function. Improvement in olfactory function was independent from the improvement in nasal airflow, indicating the crucial role of inflammatory processes in allergic rhinitis.