PIC to PIC Serial data using Cat5 cable

[skimask]

Hello,
I am currently working on a project where two PIC's on two separate boards need to communicate serially over a distance of about 5 metres. I am looking to use UTP Cat5 cable to connect them together. As well as data, this cable will also carry the power supply from board 1 to board 2.
For noise immunity, is it best to use one of the twisted pairs for the power supply and another for the data, or will it not matter too much?
Thanks,
Andy Wood

Depends on what speed and how electrically noisy the area is and are you planning on using RS232 type connection, RS485, I2C, SPI, a differential signaling method, single wire, common grounds & power (which I'd assume based on what you said)?