Can one lie when it comes to Shidduchim? for example if I know that a boy smokes cigarettes, and someone asks me does he smoke? can I say no for the sake of the shidduch, because I think this would be a good match?
The prohibition against lying applies equally to shidduchim as to all other areas of life. Just as one would not lie about a potential business partner, one may not lie about a potential life partner. Smoking is a good example. While many are willing to overlook such activity, there are many who would not consider a shidduch with such a boy.
While lying is prohibited, there are many details which may be revealed as the shidduch proceeds, and if not asked may be kept quiet for some time.