More than 300 jobs are set to be created by two companies in counties Cork and Galway.
Cork-based company Westbourne IT Global Services has announced it is to create 50 jobs over the next 18 months.
The company is a provider of secure, remote, IT support for global users.
The job creation is being supported by the Department of Jobs, Enterprise and Innovation through Enterprise Ireland.
Taoiseach Enda Kenny welcomed the announcement, saying: "The expansion of this indigenous company is a great example of how Irish businesses can compete and succeed in global markets."
Westbourne IT Global Services was founded in 1994 by John O'Sullivan and operates from two facilities in Cork.
Mr O'Sullivan said the company has "ambitious plans for continued growth over the next five years and plan to expand our workforce to 350 employees by 2019".
Also in Cork 150 new jobs are to be created by US hedge fund administrator HedgeServ. The company already employs 380 people in Dublin and 50 in Cork.
Elsewhere, a company that manufactures electronic cigarettes is to create 138 jobs in Co Galway.
Full details on the investment will be announced on Monday, but it is understood that the positions will be created at a new production facility in Corr na Móna in Connemara.
Rossport Pharmaceutical makes electronic cigarettes as well as liquids and nicotine-containing products that are used as alternatives to smoking.
The company will begin recruiting immediately and will offer opportunities in marketing, R&D, production, and pharmaceutical roles.
An investment of €5.2m in the Galway facility will be supported by Údaras na Gaeltachta.
Rossport Pharmaceuticals was established in Belfast in 2007 and currently employs 80 people.
It has a sister company that operates an e-cigarette retail business, with 20 stores across the country.
It plans further expansion in the coming 18 months and says there is a growing market across Europe for its products.
Last month, the Minister for Health said e-cigarettes should not be marketed as a consumer product.
James Reilly said in some cases they had more nicotine than light conventional cigarettes.
While accepting the benefits of e-cigarettes in helping people to quit smoking, he said nicotine was also a dangerous drug.
Amazon to move to new Dublin location
Meanwhile, online retailer Amazon has announced that it is to move its Dublin Development Centre to a new 69,000sq.ft office space in Dublin 4.
The company currently employs around 450 people in Ireland.
However, the new three-floor premises at Burlington Plaza can accommodate up to 600 staff.
The first phase of the move is expected to take place in April, when 100 existing employees will transfer. The remainder will move by June.
Amazon opened its Dublin Development Centre in 2005, where a team of engineers and developers provide support to its websites and web-based services.
The centre also hosts support and technical assistance teams for a range of other Amazon products.
Roles at the centre are in the areas of engineering, software development and technical management.
Jeff Caselden, the Managing Director of the centre, said Amazon had created hundreds of jobs in Ireland over nine years, and it had found the talent needed to continue its growth.
Amazon's growth in Ireland has been supported by the Department of Jobs, Enterprise and Innovation through IDA Ireland.