Since the introduction of antibiotics, the incidence of otitis media induced complications such as mastoiditis and subperiosteal abscess has significantly decreased. We experienced two cases. The first case is a four-year-old boy who underwent right simple mastoidectomy and myringotomy with tympanic tube insertion. During the operation, we found a lot of pus accumulated in the subperiosteal space, mastoid cavity and middle ear. Tenacious secretions and edematous mucosa blocked the aditus ad antrum. The second case is a thirteen-year-old boy who underwent modified radical mastoidectomy and type III tympanoplasty. A great amount of thick, yellowish discharge was removed from the subcutaneous tissue, subperiosteal space and mastoid cavity. The mastoid cavity and the middle ear were filled with a huge cholesteatoma which blocked the aditus ad antrum. Both patients were treated with intravenous antibiotics during hospitalization. They recovered well after their operations and had no evidence of recurrence over 13 and 5 months of follow-up, respectively.