2K Czech has revealed requirements and recommendations for Mafia 2 PC version:

MINIMUM SYSTEM REQUIREMENTS
Operating System: Microsoft Windows XP (SP2 or later) / Windows Vista / Windows 7
Processor: Pentium D 3Ghz or AMD Athlon 64 X2 3600+ (Dual core) or higher
RAM: 1.5 GB
Video Card: nVidia GeForce 8600 / ATI HD2600 Pro or better
Hard Disc Space: 8 GB
Sound Card: 100% DirectX 9.0c compatible sound card
Peripherals: Keyboard and mouse or Windows compatible gamepad

RECOMMENDED SYSTEM REQUIREMENTS
Operating System: Microsoft Windows XP (SP2 or later) / Windows Vista / Windows 7
Processor: 2.4 GHz Quad Core processor
RAM: 2 GB
Video Card: nVidia GeForce 9800 GTX / ATI Radeon HD 3870 or better
Hard Disc: 10 GB
Sound Card: 100% DirectX 9.0c compliant card
Peripherals: Keyboard and mouse or Windows compatible gamepad

PHYSX/APEX ENHANCEMENTS SYSTEM REQUIREMENTS
Operating System: Microsoft Windows XP (SP2 or later) / Windows Vista / Windows 7
Minimum Processor: 2.4 GHz Quad Core processor
Recommended Processor: 2.66 GHz Core i7-920
RAM: 2 GB

Video Cards and resolution: APEX medium settings
Minimum: NVIDIA GeForce GTX 260 (or better) for Graphics and a dedicated NVIDIA 9800GTX (or better) for PhysX
Recommended: NVIDIA GeForce GTX 470 (or better)

Video Cards and resolution: APEX High settings
Minimum: NVIDIA GeForce GTX 470 (or better) and a dedicated NVIDIA 9800GTX (or better) for PhysX
Recommended: NVIDIA GeForce GTX 480 for Graphics and a dedicated NVIDIA GTX 285 (or better) for PhysX

NVIDIA GPU driver: 197.13 or later.
NVIDIA PhysX driver: 10.04.02_9.10.0522. Included and automatically installed with the game.