Symbolism, Imagery, Allegory
Known as "cancers" in nadsat, cigarettes are what the characters puff on when they need to appear cool or nonchalant (in the case of the "modern youth"), when they are being philosophical or anxious (in the case of the prison chaplain and Rex, the cop driving Dim and Billyboy's getaway squad car), or just delinquent (the ten-year-old girls Alex rapes, all the kids at the bars, as well as Alex's entourage). What is interesting is how Burgess calls them "cancers," obviously to incite the negative connotation.