The belief smoking helps you concentrate is another myth too. Smoking simply takes away the artificially induced feeling of unease from the last cigarette. The 'need' for another cigarette only reduces it temporarily. If you had never smoked you would find that even smoking a single cigarette had the opposite affect. To repeat myself, the only reason smoking helps you concentrate is because you smoke.

Smoking reduces the oxygen levels in your blood. It also slows its flow, thus reducing the levels of nutrients and oxygen that can reach the brain. Waste products are not only increased, but are harder to remove. As you can see this does not aid concentration in any way, only impairs it. To help the subconscious mind dispel its association of concentration with smoking, do a few rounds of the following:

'Even though I smoke when I need to concentrate, and I believe it helps me, I deeply and completely accept myself'

'Even though my subconscious mind still associates the need to smoke with the need to concentrate I love and respect myself anyway'