ADSL+2 Cable Lenght Slow/Fast?

Hi Everyone,
I have ADSL+2 Broadband, i was just wondering would the internet speed slow down if i extend the cable lenght, say about 20 Meters? I want to use the internet in one of the bedroom? Im thinking of running a RJ-45 and Rj-11 cable from the lounge room to the bedroom through the roof, as the main phone line is in the lounge room. Any info. will help, Thank You.

 

Sorry my mistake, I only need to extend the phone line, not the RJ45 cable.