Background: It is well known that pulmonary alveolar proteinosis(PAP) is characterised by accumulation of surfactant lipids and proteins within airspaces. However, few previous data describe the serum lipid levels associated with PAP.Materials and methods: We retrospectively reviewed 25 patients with idiopathic PAP(iPAP). The serum lipid levels of patients with idiopathic PAP were compared with those of the healthy volunteers. In patients and healthy subjects, the LDL-C/HDL-C ratios were 2.94±1.21 and 1.60±0.70, respectively (p <0.001), HDL-C were 1.11±0.27 and 1.71±0.71 respectively (p <0.001). The values of LDL-C correlated significantly with those of PaO2 and PA-aO2 (r=-0.685, p=0.003, and r=0.688, p=0.003, respectively). The values of LDL-C/HDL-C ratios also correlated with PaO2 levels and PA-aO2 levels (r = -0.698, p = 0.003, and r =0.653, p = 0.006, respectively). 11 and 13 patients experienced respectively a decline in TC and LDL-C levels following whole lung lavage(WLL), the median decline was 0.71mmol/L(p<0.009) and 0.47mmol/L(p<0.003), respectively.Conclusions: the serum lipid levels , especially the levels of LDL-C and LDL-C/HDL-C, may reflect the severity of the disease in PAP patients, and predict the therapeutic effect of WLL.