Fungal infection of paranasal sinuses appears to be relatively rare in occurrence, but there is a rising incidence of it which accompanies with the increasing use of antibiotics, steroid hormone, anticancer drugs, and radiation. We experienced 13 cases of the paranasal sinus fungal infection which computed tomography was helpful to diagnose and they were compared with 10 cases of chronic non-specific unilateral sinusitis as control group. The characteristic feature of C-T findings in the mycotic infection was the intermixture of the high density area with the low density area in the affected sided sinuses, and it appears to be caused by the increased X-ray absorption due to the calcification. In conclusion, pertinent parameters of paranasal sinus mycotic infection which enhance the index of suspicion are : 1) Unilateral sinusitis on plain X-ray(usually only one paranasal sinus involvement). 2) Over age of 30. 3) Chief complaint except sinusitis symptoms ; facial pain, toothache, periorbital pain, etc. 4) Short duration of symptoms. 5) Calcification on C-T scan.