Highly ordered arrays of diamond cylinders with square and triangular cross sections were prepared by CVD synthesis using anodic porous alumina templates with modified pore shapes. The CVD synthesis of diamond was carried out using a microwave enhanced CVD apparatus using alumina templates. By removing the alumina template in concentrated phosphoric acid, an ordered array of cylinders with a uniform size and shape was obtained. The obtained diamond cylinders could be isolated, and yielded the shape- and size-controlled diamond particles.