The retail arm will be listed as WHSmith PLC and the distribution division will be renamed as Smiths News PLC. Shareholders will receive one share in each company for every existing share they own.
Kate Swann will be group chief executive of the new WHSmith and Alan Stewart will be group finance director. All existing board members will become non-executive directors.
Mark Cashmore will become the chief executive of Smiths News, with Alan Humphrey taking up the post of finance director.
The group said WHSmith's pension trust would be split in two, but employees' benefits would remain the same. As part of a move to reduce the company's pension deficit,£50 million will be paid into the fund. The cash will come from£70 million of borrowings by Smith News.
The demerger is still subject to shareholder approval. A meeting is anticipated in early August, with the demerger set to become effective on August 31.
WHSmith first revealed its intention to demerge the two divisions in April.
The news distribution arm has a 36 per cent market share in the newspaper wholesaling sector and a 39 per cent share in magazines.
WHSmith Retail has a 3 per cent share in newspaper sales. Independent retailers account for 62 per cent of sales. In magazines, WHSmith Retail has an 18 per cent share, with independents accounting for 34 per cent.
Swann said: 'Both businesses will benefit from increased focus on their respective strategies.'
In a statement, the group said present trading was satisfactory. It remains cautious about the outlook for consumer spending, but said trading was in line with management expectations and the board remains confident in the outcome for the full year.