The sinuses include one pair each of the maxillary, septal, frontal, and pterygoid sinuses that surround the nasal cavity. Sinus cysts are common benign lesions, some of which require surgical treatment. Most of the maxillary and pterygoid sinus cysts are plasmacytic cysts, which are like balloons with fluid inside and slowly increase in size in the sinus cavity, and most of them do not produce symptoms and can be observed conservatively without surgery or medication. Very few of them will rupture on their own, and a yellowish, clear fluid will flow from the nasal cavity. A small number of patients will develop local pressure or headache, and these patients can be treated surgically. Surgery is mostly done endoscopically in the sinuses with minimal damage. Mucous cysts are common in the septal sinuses and relatively uncommon in the frontal sinuses. These cysts are mucous membrane-encapsulated mucous secretions that slowly increase in size and produce symptoms by compressing the surrounding tissues. Most commonly, they produce ocular symptoms such as proptosis, diplopia, and loss of vision. These cysts require prompt surgical treatment to avoid adverse consequences. Most cysts are plasmacytotic and most of them do not require surgical treatment. The cysts are benign lesions and do not become malignant. There are also some rare cysts affecting the sinuses, such as dermatomal cysts and tooth-containing cysts, which do not essentially originate from the sinuses, but a few of them protrude into the sinus cavity adjacent to the sinuses, and these require surgical treatment.