Have you installed the latest Mountain Lion ready drivers for the unit?

When you are adding the printer, what options are you using to choose the drivers?

If you choose "Auto Select" from the "Use" drop down that may be your issue.

If you choose "Select Printer Software" does the Canon software show?

First to do: check if your printer is supported by Apple. It was not true in my case, but may be true in yours.

There are at least two opensource driver packages, supporting the printers which are abandoned by their vendors:

SpliX.

a set of CUPS Printer drivers for SPL (Samsung Printer Language) printers. If you have a such printer, you need to download and use SpliX.

Supported Printers

• Dell 1100, 1110
• Samsung CLP-200, CLP-300, CLP-500, CLP-600, CLP-610, CLX-216X, CLX-2170, CLX-3160, ML-1510, ML-1520, ML-1610, ML-1630, ML-1710, ML-1740, ML-1750, ML-2010, ML-2150, ML-2250, ML-2510, ML-2550, ML-2571, ML-3050, ML-3560
• Xerox Phaser 3115, 3116, 3117, 3120, 3121, 3122, 3130, 3150, 3420, 3425, 5500, 6100, 6110

Samsung-GDI for Mac OS X

Supported Printers

• Generic GDI Printer
• Lexmark
• Samsung ML-200, ML-210, ML-1000, ML-1010, ML-1020, ML-1200, ML-1210, ML-1220, ML-1410, ML-1430, ML-1440, ML-1510, ML-1520, ML-1610, ML-1710, ML-1740, ML-1750, ML-2010, ML-2150, ML-2250, ML-2550, ML-4500, ML-5080, ML-6040

Personal experience

I first installed SpliX and it worked well with documents printed from MS Word or PDFs. But it failed with printing .jpg images from Preview app or command-line lpr utility. So I switched to Samsung-GDI, which handles .jpg well.

Also, if a printer is set up twice with different drivers it doesn't work with any of them. So you should only have one printer in Settings > Printers (per each device). You can have both driver packs installed on your system, though.

Similar problem was discussed in Xerox 3117 driver for OS X Yosemite