A vehicle cargo compartment assembly is provided that has a vehicle floor defining an opening for a storage compartment and a lid sized for covering the opening and moveable between a closed position and an open position. A cargo mat has a body portion overlaying the lid and is moveable with the lid between the closed position and the open position. An outboard flap extends beyond the lid to overlay a portion of the vehicle floor bordering the opening when the lid is in the closed position. The outboard flap is supported by the vehicle floor when the lid is in the closed position, and the outboard flap is hinged to the body portion such that the outboard flap extends downward at a hanging angle with respect to the body portion when the lid is in the open position.