Residual risk of cardiovascular events after treatment with stain might be explained in part because patients have low levels of n−3 polyunsaturated fatty acids (PUFA). We examined how lipid-lowering therapy with strong statin affected serum PUFA levels in patients with coronary artery disease. The study population consisted of 46 patients with coronary artery disease whose low-density lipoprotein (LDL) cholesterol was more than 100 mg/dl. Lipid-lowering therapy was performed with a strong statin including atorvastatin (n = 22), rosuvastatin (n = 9) or pitavastatin (n = 15). Serum PUFA levels were determined by gas chromatography. The treatment with strong statin decreased the sum of dihomo-γ-linolenic acid (DGLA) and arachidonic acid (AA) levels (195 ± 41 to 184 ± 44 μg/ml, P < 0.05) as well as the sum of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels (233 ± 71 to 200 ± 72 μg/ml, P < 0.001). These effects of strong statin resulted in a significant decrease in ratio of the sum of EPA and DHA levels to the sum of DGLA and AA levels (1.20 ± 0.27 to 1.10 ± 0.35, P < 0.05). The percent decrease in the LDL cholesterol level correlated significantly with that in the sum of EPA and DHA levels (r = 0.38, P < 0.01). In conclusion, our results showed that lipid-lowering therapy with strong statin mainly reduced n−3 PUFAs in proportion to the decrease in the LDL cholesterol level in patients with coronary artery disease.