How will smoking two cigarettes a day effect CO2 laser resurfacing ?

Cigarette smoking, in any amount, effects the healing process from surgery or procedures like chemical peels and laser resurfacing.  The best results would be achieved without any cigarette smoking.  If you did smoke, you could compromise your results.  

As others have noted, smoking will only slow your healing down.  Nicotine serves as a vasoconstrictor which impedes blood flow to your skin and carbon monoxide (released in the smoke) competes with binding sites on your red blood cells.  Both of these factors diminish oxygenation of your skin and impair healing. If you commit yourself to doing a procedure like laser resurfacing, it makes sense to take every step necessary to allow for predictable wound healing.

Smoking will negatively effect any surgical procedure, especially those that impact skin. Smoking reduces the concentration of oxygen in regions that are healing from laser treatments and slows the healing of surgical wounds. You must also avoid second hand smoke as this has the ability to further slow the healing process. Furthermore you should consider the benefits of quitting smoking as it will reduce the need for further skin treatments. The combination of sun exposure and smoking has proven to require more intensive treatments with prolonged exposure to either.