We performed a retrospective study that compared the efficacy and safety of dexamethasone (DEX) 8 mg with DEX 16 mg in cases of acute and delayed emesis induced by cisplatin (CDDP) chemotherapy in patients with lung cancer. Sixty-eight lung cancer patients treated with combination cisplatin, ifosfamide, and irinotecan therapy were studied. The DEX 8 mg group and the DEX 16 mg group received DEX intravenous injection 30 min prior to CDDP. All patients then received a 5-HT(3) antagonist intravenous injection 30 min before CDDP. Protection from acute nausea (day 1) was significantly superior in the DEX 16 mg group compared with the DEX 8 mg group (DEX 8 mg, 76.5%; DEX 16 mg, 100%). Protection from delayed emesis (day 1) was significantly superior in the DEX 16 mg group compared with the DEX 8 mg group. There was no reported severe nausea (grade 3) and vomiting (grade 2) in the DEX 16 mg group. Furthermore, perphenazine hydrochloride for use as rescue medication was required by significantly fewer patients in the DEX 16 mg group than in the DEX 8 mg group (DEX 8 mg, 41.2%; DEX 16 mg, 0%). Adverse effects were observed in 10 cases (nine reports of generalized fatigability, two of headache) in the DEX 8 mg group and in 16 cases (11 reports of generalized fatigability, one of pruritus) in the DEX 16 mg group. However, because the symptoms were all mild, we did not consider that there was any safety problem. In conclusion, DEX 16 mg is a clinically useful treatment for acute and delayed emesis induced by cisplatin-induced chemotherapy in patients with lung cancer.