GSTM1 and polycythemia: Hb and Hct values decreased in smokers who quit smoking compared to baseline values at 3 months (<i>p</i> < 0.05).<h4>Conclusions</h4>Of the patients with polycythemia, 65% were current smokers and about half of them were successful in quitting smoking at 3 months with effective implementation of smoking cessation interventions.