In a short statement to London’s Alternative Investment Market, Vimio said Mr Rooney has left having assisted with the flotation on the exchange last year.
“The board of Vimio would like to thank Mr Rooney for his significant contribution to date and would like to wish him every success in the future,” it said.
Attempts to contact Mr Rooney for comment yesterday were unsuccessful.
He joined Vimio, which develops software that allows mobile phones to broadcast live television, ahead of the flotation last September. He was on a salary of €50,000 a year, but did not have a stake in the company.
It is the third time in less than five years that he has left a high profile role.
He was chief executive of Baltimore Technology but resigned in late 2001 after the company’s share price began to collapse.
He also served an 18-month stint as chief executive of the Football Association of Ireland.
David McKenna, Vimio business development director, has been appointed interim executive chairman. Mr McKenna previously headed Marlborough Recruitment, which went bust in 2002.
Shares in Vimio were unchanged at 160 pence (234 cents) yesterday. They have gained more than 60% since the company went public last year.
In December, Vimio announced its maiden interim results, posting a loss of €1 million in the six months to end September 2005.