Some characters of amphidiploid lines (2n=38 AACC) and sesquidiploid lines (2n=29 AAC) derived from Brassica rapa var. pekinensis (2n=20 AA) and B. oleracea var. capitata (2n=18 CC) were investigated and the effect of the C genome was studied in this report. Characters, such as plant habit, plant height, head height, head type, leaf type, outer leaf wax and midrib type etc. in the sesquidiploid lines were close to those of the respective A genome lines, whereas in the amphidiploid lines they were close to those of the respective C genome lines. C genome showed a significant dosage effect for the characters studied. Appearance of outer leaf and incisions of leaf in the amphidiploid and the sesquidiploid lines were the same as those in the respective C genome lines. Heterosis was found in interspecific hybrids for the weight of total leaves and head leaves. Dosage effect of the C genome was also found for these two characters. With the decrease in the head index, amphidiploid lines and sesquidiploid lines showed an increase in the number and weight of outer leaves and decrease in the edibility rate. Dosage effect of the C genome was detected for the Brix value of the edible parts. Principal component analysis was carried out for 19 characters with the accessions of heading type. Results showed that the first component was mainly related to the morphological characters. The second component was principally concerned with yield. Both the first and second components showed the dosage effect of the C genome genotypes used in this study. Heterosis was found for the second component in the interspecific hybrids.