The relation between chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) has been largely undescribed and the occurrence and frequency of anemia in COPD has rarely been studied, so the aim of this study is: to estimate the frequency of undiagnosed CKD among COPD patients and to verify whether concealed CKD is prevalent in COPD population, and to assess the frequency of anemia in COPD patients and its relation to the severity of the disease. Patients and methods: this study included 100 stable COPD patients with various degrees of severity. They were divided into 2 groups: group (І): patients with mild to moderate severity of COPD (n=43) and group (П): patients with severe to very severe COPD (n= 57). All studied patients were subjected to: pulmonary function tests, complete blood count, erythropoietin level measurement, glomerular filtration rate measurement, and arterial blood gases analysis. Results: there was a statistically non- significant increased frequency of concealed chronic renal failure (CRF) in patients of group (П) than that of group (І). But a significant increased frequency was seen in overt CRF in patients of group (П) than that of group (І) with a statistically significant positive correlation between COPD severity and renal function reduction . As regards the frequency of anemia, there was a statistically significant high frequency of anemia in patients of group (П) than that of group (І) with a statistically very highly significant negative correlation between COPD severity and hemoglobin level. Conclusions: 1) CRF occurs in high rates in COPD patients and it is related to the disease severity. 2) Anemia is a frequent co-morbidity among COPD patients especially in those with severe disease.