Paraneoplastic nephrotic syndrome has been reported in various malignancies: malignant lymphoma, colon cancer, lung cancer, and prostate cancer. Of these, lung cancer is the most commonly associated with the syndrome. Here, we report 4 cases of nephrotic syndrome associated with lung cancer, in one of which urinary protein and edema were improved by steroid therapy. These results suggest that in patients with paraneoplastic nephrotic syndrome histologically diagnosed as having minimal change disease (MCD), it is important not only to treat the cancer itself but also to use steroids as early as possible. On the other hand, our results also showed that treatment is still difficult for locally advanced or metastatic tumors. Therefore, when we encounter patients with nephrotic syndrome, it is important to be aware of the association of nephrotic syndrome and lung cancer.