Accurate estimates of leaf area index (LAI) and leaf angle distribution (LAD) are important for estimating the exchange of energy and gases in vegetative canopies. Direct estimates of LAI and LAD are laborious, time consuming and often times destructive. Stewart and Dwyer [Agric. For. Meteorol. 66 (1993) 247] introduced a mathematical method to calculate LAI and LAD of maize canopies based on descriptions of leaf width and leaf curvature. However, the method is limited in its application. The objectives of this research are to: (1) extend the method to account for leaves with maximum curvature height at the leaf tip (i.e., straight leaves, which commonly occurs with leaves at the top of maize canopies), so that the method provides a general application to maize canopies, and (2) test the performance of the extended model. LAI and LAD simulated using the mathematical method were tested against observed LAI and LAD values. Average leaf width coefficients, determined from all leaf positions, were used in the leaf area calculation. Leaf area simulations agreed overall within 2% (51 cm2) of observed leaf area values. Estimated LAD agreed within 5% of the field observed LAD. The method offers a straightforward, reliable means of estimating LAI and LAD, when the appropriate coefficients are known, without requirements for special instrumentation or other conditions. The method also offers a means of checking the performance or reliability of other methods of characterizing canopy structure.