Abstract. The role of low-volatility organic vapors in atmospheric new particle formation has been studied based on a data set of 17 nucleation events observed during the CAREBeijing 2008 campaign. The particle formation rates show good correlations with sulfuric acid and organic vapors implying that both play an important role in the atmospheric new particle formation. High correlation coefficients are observed in all investigated nucleation mechanisms. The best fit (R = 0.73, slope = 1.1) between the observed and modelled particle formation rates is achieved with the homogenous nucleation theory of sulfuric acid (both homomolecularly and hetermolecularly) with separate coefficients in J=KSA1[H2SO4]2+KSA2[H2SO4][Org]. The contributions of the sulfuric acid and the organics involving terms have been 43% and 57%, respectively. In addition, the higher particle formation rates are observed on polluted nucleation days, indicating the organic vapors should be involved in the new particle formation process in the polluted urban environment of Beijing with high background aerosol loading.