We investigated the properties of field emission from a pillar array of aligned carbon nanotube (CNT) bundles, which were fabricated on a Si substrate by thermal chemical vapor deposition. To explore the influence of the pillar arrangement on its field emission, the ratio of interpillar distance ( R) to pillar height ( H), R/ H, was investigated as a function of H by changing H while maintaining R at 100 μm. The most-enhanced field concentration was obtained at R/ H ∼ 6, although we previously reported that the optimal configuration of pillars for R = 250 μm was a ratio of R/ H = 2. These results show that the optimal R/ H for greatest field emission from the CNT pillar array is dependent on R.