Corn (Zea mays L.) produced in narrow rows can increase yields and result in a quicker canopy closure. Costly equipment modifications make narrow rows impractical, but a twin row configuration may boost production with fewer equipment modifications. We compared yield and leaf area index (LAI) for a conventional and a glyphosate-tolerant hybrid across three plant populations (low 39000-44000; medium 64000-69000; high 79000-84000 plants ha-1) in two row patterns (single vs. twin) at four locations during the 2005 growing season. The experimental design was a RCB (r = 4) with a split-split plot restriction on randomization, where corn hybrids were assigned to main plots, row patterns to subplots and plant populations to sub-sub plots. There was a noticeable and statistically significant interaction between hybrid and population at three out of four locations. The conventional hybrid yielded 15% (8.6 vs. 7.3 Mg ha-1), 12% (9.9 vs. 8.7 Mg ha-1), and 16% (8.7 vs. 7.3 Mg ha-1) higher than the glyphosate-tolerant hybrid at the medium population. Across locations, the conventional hybrid generally yielded higher at the low and medium population, while the glyphosate-tolerant hybrid yielded higher at the high population density. Row spacing did not affect yields. Corn yields did not always increase with increased populations. At two locations, LAI values of the twin row pattern were 13% (3.1 vs. 2.7 m2 m-2) and 10% (3.3 vs. 3.0 m2 m-2) higher than the standard row pattern. Leaf area index generally increased with increased plant populations and twin row configurations. Twin row corn resulted in a faster canopy closure, but corn yields were not influenced by row pattern.