Two previously uncharacterized Vitis vinifera CONSTANS-like genes (VvCO, VvCOL1), which are predicted to encode proteins with homology to members of the Arabidopis CONSTANS family, were identified. Under controlled conditions, both genes show a diurnal expression pattern with peak at dawn. During grapevine bud development, VvCOL1 is mainly expressed in dormancy, suggesting a participation in the transcriptional photoperiod control of bud dormancy induction and maintenance in this species. On the other hand, VvCO expression in latent buds is in agreement with a function during flowering induction. A spatial and temporal relationship in the expression of VvCO, VFY and VvMADS8 (the Arabidopsis LEAFY and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 orthologues) in latent buds is observed, suggesting that these genes are involved in the seasonal periodicity of flowering in grapevines. Furthermore, our results provide a new molecular insight into tendril development showing that grapevine CO homologues are also expressed in this distinctive organ.