The invention relates to a new catalyst component for the polymerization of olefins comprising a compound of formula CyLMZp, wherein M is a Group 4-6 metal, Z is an anionic ligand, p is the number of anionic ligands, Cy is a mono- or poly-substituted cyclopentadienyl-type ligand and L is a guanidinate ligand of the formula wherein: each A is independently selected from nitrogen or phosphorus and R, R1, R2 and R3 are independently selected from the group consisting of hydrogen, hydrocarbyl, silyl and germyl residues, substituted or not with one or more halogen, amido, phosphido, alkoxy, or aryloxy radicals. The invention also relates to a catalyst system for the polymerization of olefins and a process for the polymerization of at least one olefin having 2 to 20 carbon atoms.