Inflammatory myofibroblastic tumor (IMT) is a rare condition that can mimic potentially more dangerous states such as malignant tumors. The tumor itself can also show a local malignancy as well as malignant transformation. The paranasal sinus IMT is quite a rare case in the literature. The manifestation of the disease can include a face swelling, nasal obstruction, epistaxis, vision acuity worsening, numbness of face, pain. Etiology of this type of lesion still remains uncertain but there are a few assumptions on the issue: viral and genetic among the others, as well as posttraumatic and postinflammatory. We report the case of an adult woman with IMT detected in right maxillary sinus after endoscopic sinus surgery.