Background. Smoking is the most dangerous modifiable risk factor all over the world and requires the lowest cost to quit. Objectives. In this study, we aimed to determine the relationship between the Fagerström Test for Nicotine Dependence (FTND) and carbon monoxide (CO) levels and neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), monocyte/lymphocyte ratio (MLR) and RDW, WBC, MPV values. Material and methods. 138 participants who applied to the Smoking Cessation Clinic of Bolu Izzet Baysal Training and Research Hospital between January 2022 and March 2022 were included in our study. After obtaining the necessary consent, the FTND test and CO levels in expiratory air were measured. The required haematological values of the participants were evaluated. Results. It was found that there was statistical significance between the CO levels of the participants and their FTND scores, and it was observed that the FTND scores increased as the CO level increased (p = 0.000). There was a statistically significant correlation between CO levels and PLR ratios and WBC levels (p = 0.024, p = 0.000). It was determined that as the CO level increased, the PLR ratios decreased, and the WBC values increased. Conclusions. In our study, a positive correlation was found between FTND levels and exhaled CO levels. We can say that CO levels can be a marker in predicting the level of addiction. In addition, it was observed that there was a significant relationship between exhaled CO levels and FTND levels, as well as PLR and WBC values.