why does the scan take so long on my mac

Hello adragonfly13
 
Welcome to the Webroot Community,
 
I have an older Mac and running Webroot the scan takes about 1 hour and 20 minutes. New Macs take 10 minutes to scan.
 
May I ask if you have the Time Machine or an external back up running? Or do you have scan mounted drives checked?
 
If so please uncheck Scan Mounted Drives. Then rescan.

 
You can open Webroot and click on the Advanced Settings in the right hand corner..
 
This is how I handle my Mac system with Webroot below:  
 
http://live.webrootanywhere.com/content/553/Changing-Scan-Settings because scanning the Mounted drives will take days.
 

 
Scanning Time Machine backups can take an extremely long time due to the way that apple backs up the information.  Webroot does certain kinds of traces that will open every single binary on the disk to make sure it is safe, this however can take a really long time on Time Machine.  I would recommend changing your settings so that you do not scan mounted drives with WSA. I
 
Here is the Mac User Guide  Also you can Submit a Support Ticket free of charge if you have any concerns and they can certainly check this out for you.