Lams, who had been at since September 2004, has gone to Australia, which also means a promotion for Teresa Pereira.
Pereira, previously UK and pan-European trade marketing manager, steps up to European trade marketing director.
The appointments were made by Javier Rodriguez Zapatero, who was recently installed in the newly created role of vice-president of European sales.
Zapatero said: "I am extremely pleased to see these positions filled by internal candidates. They demonstrate the depth of talent we have at Yahoo! and prove the will of the company to promote internal mobility and offer strong career paths for staff."