The company already stocks confectionery but has added pick ‘n’ mix to a small number of its stores.
Experts said Woolworths’ sales in this area were worth between £200m and £300m a year before its collapse.
Retail Knowledge Bank senior partner Robert Clark said: “Even if WH Smith picks up just £50m to £60m worth of this, it’s not to be sniffed at. And there’s space available in WH Smith stores with the slimming down of its entertainment offer.”
WH Smith said: “We are trialling Pick ‘n’ Mix in a small number of our stores. The offer builds on our established confectionery offer.”