Cigarette consumption during pregnancy produces deleterious effects in both, mother and fetus, some of them due to the presence of toxic elements in cigarette smoke, such as cadmium. Placenta constitutes a dual-purpose specimen for evaluating the pollutant burden exerted on the mother as well as on the fetus. The main objective of this study was to establish a correlation between placental concentration and distribution of some metal elements and birth weight of neonates delivered by mothers, who were either moderate smokers or nonsmokers. Forty nonsmoking and moderate smoking pregnant women paired per age, parity, weight, height and body mass index were selected. Smoking was assessed by self-reported cigarette consumption during pregnancy and urine cotinine concentration before delivery. Placental metal concentrations were evaluated by atomic absorption spectrometry (copper and cadmium) and neutron activation analysis (zinc and iron). Newborns from smokers had lower birth weights compared to infants from nonsmokers. Birth weights were correlated with placental cadmium concentrations in both, smokers and nonsmokers. Placental zinc and cadmium of smokers were mainly located at the maternal side and their levels were higher than those found in nonsmoker's placentas. In addition, all metal nutrient/pollutant ratios were decreased in the smoker group. In this first study performed in our region, we found that moderate smoking mothers deliver neonates with decreased birth weight and highly correlated to placental cadmium concentration. Decreased metal nutrient/pollutant ratios, a condition here found in smokers, may indicate a placental dysfunction, contributing to impair birth weight.