Abstract: A new family of palladium based metallization catalyst compositions is diosed.These catalysts are used in a process for the selective deposition of a metal on a substrate when a metallization mask (i.e. a plating resist) is used over the substrate.Processes and compositions are also disclosed for manufacturing printed circuit boards, by using two metallization sequences, or one alone the latter comprising a so-called "selective process."The process and composition are generally employed for the electroless plating of substrates, namely the metallization of plastics, ceramics, anodized aluminum and other materials.