The trial was carried out in 2003-2005. Working hypothesis was tested in pot experiment, where maize plant mass above the ground and roots was evaluated at phase of 4-5 leaves. Germination potential was evaluated in cold test. Field trials in 2004 and 2005 were established to evaluate plant health and yielding. Three seed fractions from the same seed lot of hybrid Clarica were tested (TKW 261g, 299g and 336g). Biochicol 020PC was used as seed dressing with 5% solution and spray of plants at stage of 5-6 leaves at dose of 3 l/ha. Biochicol 020PC did not cause significant changes in maize plants development and heath condition. The tendency was observed to shorten roots at phase of 4-5 leaves, increase fresh and dry matter of both above and below ground part of seedlings and decrease of yield. Seed size significantly influenced cold test results and field germination. Number of normal seedlings decreased as TKW increased. Seedlings developed from the smallest and medium seed fractions had longer roots compared with those from largest fraction. Fresh and dry matter of above ground plant parts and roots of plants in 4-5 leaves stage increased with TKW. Yielding depended on fraction and decreased as TKW increased.