If you smoked regularly, the following would happen
1) Pulmonary function would decrease, which would reduce capability of your lungs (alveoli) to transfer o2 and co2 in and out of your blood respectively.
2) This would probably mean that your body tissue would probably be used to surviving on low oxygen (chronic hypoxia) due to your smoking, so you would probably fare well at high altitudes where o2 is low.
3) Also due to this chronic hypoxia, your haemoglobin or red cell mass concentration would increase in an attempt to compensate for the low o2 content of your blood. A higher haemoglobin concentration basically increases the capacity of bloody to carry oxygen, (smokers are found to have higher haemoglobin concentrations). This would make making it easier to acclimatise at higher altitudes.
4) Also since smokers generally have higher co2 and 2-3 DPG content in their blood, the haemoglobin generally will have decreased affinity for o2 and therefore give it up easily to respiring tissues, thus once again making it easier to acclimatise at higher altitudes. (This factor would depend on whether you continued to smoke at high altitudes and how much you smoke)
5) BUT since smoking increases your carbon monoxide content of your blood which can decrease the capacity of your bloody to carry oxygen which in turn will make you more tired. (This factor would depend on whether you continued to smoke at high altitudes and how much you smoke)
Therefore generally at higher altitudes a smoker will initially and generally fare off better then a non smoker. But there are other factors involved, age, sex, fitness, genetics, diet, how many cigs your smoke, etc so its not clear cut as I've made out to be.
And if any kids are reading this SMOKING IS BAD FOR YOU. We spend 99% of our lives at low altitude so smoking would be of no advantage. And if a smoker and and a non smoker spent a considerable amount of time in high altitudes, due to chronic hypoxia the red cell mass of both would increase considerably and since the non smoker should have better lungs the difference in both of them surviving at higher altitudes should even out.