It is impossible for your healthcare provider to know whether you will develop insomnia while taking Zyban. Also, in some cases, if a person does develop insomnia, it is difficult to know whether the insomnia is due to Zyban or is a side effect of quitting smoking.
If you are taking Zyban and insomnia becomes a problem, talk with your healthcare provider. There are other treatments that he or she may be able to recommend, including adjusting your Zyban dosage or trying another medicine for smoking cessation.