Nutrient deficiency in cassava can be diagnosed by plant tissue analysis with a chemical method. However, the chemical method is time-consuming and required a large number of plant samples. Synchrotron-based XRF (SR-XRF) technique has been exploited to study the content and localization of mineral nutrients in plant tissues. The mappings of mineral nutrient distributions in plant leaves may relate to leaf positions or leaf veins, especially in the nutrient-deficient leaves. The objectives of this research are to study K and Fe status and to determine K and Fe relationship with leaf positions or leaf veins in cassava using the XRF technique. The field experiment on cassava was conducted using a randomized complete block design (RCBD) with four replications. Treatment included three methods of fertilizer applications: 1) Control (no fertilizer), 2) N+P + K application, and 3) N+P+K+ micro-nutrient application. Leaf K and Fe were analyzed by chemical technique and SR-XRF technique. The result showed that, with the chemical analysis, leaf K and Fe contents in control were in the deficient range. While those in treatments adding nutrients, K and Fe were in the sufficient range. The SR-XRF technique analysis results showed a similar trend as chemical analysis. The mapping of K and Fe distribution on leaves showed that variation of count K and Fe in control was less than those in the fertilizer added treatments. The distribution of K and Fe in leaf samples of control and fertilizer added treatments had no relationship with leaf positions and leaf veins. However, when a further investigation was done in K and Fe severely deficient leaves, the Fe and K distribution tended to relate with the leaf veins.