Both low back pain (LBP) and obesity are common public health problems, yet their relation remains controversial. The aim of this study was to investigate the associations between weight-related factors and the prevalence of LBP in young adults in Finland. Participants in the ongoing Cardiovascular Risk in Young Finns Study aged 24-39 years were included (N = 2,575). In 2001, 31.2% of men and 39.5% of women reported LBP with recovery within a month or recurrent or continuous pain during the preceding 12 months. For women only, those with higher body mass index, waist circumference, hip circumference, waist-to-hip ratio, serum leptin level, and C-reactive protein level showed an increased prevalence of LBP. With all weight-related factors in the model, only waist circumference was related to LBP in women. For women, the odds ratios of LBP were 1.2 (95% confidence interval: 0.8, 1.8) for a waist circumference of 80-87.9 cm and 1.8 (95% confidence interval: 1.0, 3.2) for a waist circumference of > or =88 cm compared with a waist circumference of <80 cm. This association was independent of C-reactive protein, leptin, and adiponectin levels. The authors' findings in a relatively young population suggest that abdominal obesity may increase the risk of LBP in women.