Culex pipiens mosquito is a well-known vector of many vector-borne diseases such as filariasis, Rift Valley Fever and West Nile Fever. This study aimed to compare the resistance by World Health Organization (WHO) and Center for Disease Control and Prevention (CDC) methods. Culex pipiens larvae were collected from Qalubiya governorate and colonized with the laboratory population. Larvae were treated with different concentrations of three insecticides, lambda-cyhalthrin; diflubenzuron and chlorpyrifos. The mortality percent, as well as the parameters of regression analysis including LC50 and LC90, were calculated separately for both WHO and CDC methods. The results showed that in the case of laboratory population LC50 values were 0.000043, 0.000089 and 0.00535 ppm for lambda-cyhalthrin, diflubenzuron and chlorpyrifos, respectively for WHO method. While LC50 in CDC method were 0.0000094, 0.0002 and 0.005 ppm of the tested insecticides, respectively. From the previous results, we concluded that lambada-cyhalothrin was the most effective insecticide followed by diflubenzuron and chlorpyrifos. Also, based on the lethal concentrations (LC50 and LC90) there was difference between two methods against the laboratory population in all insecticide treatments. On the other hand, there was no difference between the two methods against the field populations except the lambda-cyhalthrin treatment. According to calculated resistance ratio (RR), all tested insecticides recorded low RR in both two assays however, results showed that chlorpyrifos displayed the highest RR value in both WHO and CDC assays. The slopes obtained for both assays were almost like each other indicating the promising of the two assays.