When the air stream does not reach the olfactory area through the olfactory fissure, olfactory dysfunction may first arise. The olfactory fissure may be closed by structural changes such as a high-sited septum deviation or a bullous middle turbinate as well as by mucopurulent secretions produced by rhinosinusitis. In cases of chronic rhinosinusitis, the decrease or closure of the olfactory fissure is virtually evident. The purpose of this study was to investigate the relation between the patency of olfactory fissure, which we categorized adhered, contact, moderate and wide type, and olfactory dysfunction. We studied 104 cases which needed the reconstruction of olfactory fissure, mainly including chronic sinusitis with or without nasal polyposis and high deviation of septum. We also compared the result of pre and post operative 4 weeks, 8 weeks, measuring by T & T transnasal and intravenous olfactometry. As a result, there was significant improvement of olfactory threshold especially in adhered type of olfactory fissure. We assumed that the reconstruction of olfactory fissure would make an improvement of olfactory function at least in conductive olfactory dysfunction and considered that olfactory threshold may be one of parameters assessing the result of nasal surgery.