A write-once optical recording medium, a method for allocating a defect management area of the write-once optical recording medium, and a method for allocating a spare area of the write-once optical recording medium are provided. A method of managing defects on a write-once optical recording medium having at least one recording layer includes the steps of allocating at least one temporary defect management area having a fixed size and at least one temporary defect management area having a variable size to said optical recording medium, respectively, recording defect management information on the at least one temporary defect management area having a fixed size and the at least one temporary defect management area having a variable size; and using the at least one temporary defect management area having a fixed size and the at least one temporary defect management area having a variable size is provided herein.