Warren has moved to H&K's Singapore bureau as executive vice-president and technology practice director to hone the division.
Smith relocates to China having spent the past eight years heading H&K's Ottawa Canada office as senior vice-president, public affairs, and deputy general manager.
'I see great things for Hill & Knowlton China over the next few years,' he said.
Smith added that despite his additional vice-president title - which is also held by other MDs and senior practice heads at H&K - his chief focus at this time is the local China market.
In his new role, Smith will report to H&K Asia-Pacific president and chief executive Brian West.