The role of across-firm differences in product quality and firms' competitiveness in determining the spatial patterns of within-product export unit values across destinations is examined in this paper. Using product level export data, it is shown that the average export unit value of a product shipped from the USA or Korea increases with distance and decreases with destination market's size. However, within-product average unit values for products exported from China and India decrease with distance and increase with market size. To interpret these different spatial patterns of unit values across exporting countries, model of quality heterogeneity is developed in which firms differ in their workers' skill level and higher-skilled workers show greater productivity in performing tasks that improve product quality. The model predicts that in relatively skill-abundant countries, exporting firms specialize in high-quality products using relatively cheap skilled labor, whereas, in relatively skill-scarce countries, firms that produce lower-quality products are more competitive.