As salam u 'alaikum... Can we pray in clothes having pack of cigarettes in pocket?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

First of all, smoking is forbidden due to the harm that it causes and due to immoderation.  Almost all scholars in this era agree that it is forbidden.

As regards praying while having cigarettes in one's pocket, the prayer is valid because even though the cigarettes are forbidden, they are not impure; and what is forbidden is not necessarily impure.

For more benefit on the ruling of smoking, please refer to Fataawa 81589 and 81345.