Objectives: High mammographic breast density (MBD) is one of the strongest breast cancer risk factors. The results of some epidemiological studies suggest that one of the lifestyle factors likely altering breast density is cigarette smoking. The aim of this study was to assess the association between active smoking, considering in detail the duration and intensity of smoking, and MBD among Polish women. Material and Methods: A cross-sectional study included 467 women aged 40–60 years who underwent screening mammography in Łódź, Poland. Volumetric mammographic density, fibroglandular tissue volume and non-fibroglandular tissue volume were determined based on the analysis of mammographic image (in the “for processing” format) using Volpara Imaging Software. Current and lifetime intensity of cigarette smoking was assessed based on the data from interviews. Linear and logistic regressions were fitted with estimated MBD parameters as the outcomes, and life-long smoking duration and intensity as the determinants, adjusted for major confounders. Results: The former smokers had a significantly lower volumetric mammographic density compared to the non-smokers in the crude analysis (p = 0.022). However, the associations became insignificant after adjustments for important confounding factors. The analyses adjusted for important confounders revealed an inverse statistically significant association between the number of pack-years and volumetric mammographic density among the current smokers (p = 0.048). Conclusions: The observed result is consistent with the majority of previous studies that analyzed the associations between mammographic density and life-long smoking duration. Int J Occup Med Environ Health. 2021;34(6):805–15