Exhibit 8.1

Principal Subsidiary Undertakings and Associated Undertakings

The following are the principal subsidiary undertakings and
the associated undertakings of eircomGroup as of 31 March 2006.



|                                                       |  |                                 |  |                                                                          |  |                                                                     
|------------------------------------------------------ |  | ------------------------------- |  | ------------------------------------------------------------------------ |  | --------------------------------------------------------------------
|Name                                                   |  | Proportion ofShare Capital Held |  | Nature of Business                                                       |  | Registered Office and Country of Incorporation                      
|Principal Subsidiary Undertakings                      |  |                                 |  |                                                                         
|                                                       |  |                                 | 
|Valentia Telecommunications (unlimited public company) |  | 100%                            |  | Holding company                                                          |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircomFunding (unlimited public company)               |  | 100%                            |  | Financing company                                                        |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircomLimited                                          |  | 100%                            |  | Provision of telecommunications and related services                     |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|Meteor Mobile Communications Limited                   |  | 100%                            |  | Provision of mobile telecommunications and related services              |  | 4030 Kingswood Avenue, Citywest Business Park, Dublin 24, Ireland.  
|                                                       |  |                                 | 
|Irish Telecommunications Investments Limited           |  | 100%                            |  | Telecommunications financing and treasury management                     |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircom(U.S.) Limited                                   |  | 100%                            |  | Marketing of telecom services in USA                                     |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|Osprey Property Limited                                |  | 100%                            |  | Property Development Company                                             |  | Leitrim House, Upper Stephens Street,
Dublin 8.                    
|                                                       |  |                                 | 
|Eirtrade Services Limited                              |  | 100%                            |  | Provision of electronic trading services                                 |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircomPhonewatch Limited                               |  | 100%                            |  | Installation, monitoring and maintenance of residential security systems |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|Indigo Services Limited                                |  | 100%                            |  | Provision of internet services                                           |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircom(UK) Limited                                     |  | 100%                            |  | Provision of telecommunications and related services                     |  | South Quay Plaza II, 183 Marsh Wall, London E14 9SH, United Kingdom.
|                                                       |  |                                 | 
|Lan Communications Limited                             |  | 100%                            |  | Systems integrator                                                       |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircomInvestments BV                                   |  | 100%                            |  | Investment holding company                                               |  | Strawinskylaan 3105 1077 ZX, Amsterdam, The Netherlands.            
|                                                       |  |                                 | 
|Eircable Limited                                       |  | 100%                            |  | Investment holding company                                               |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircomHoldings Limited                                 |  | 100%                            |  | Investment holding company                                               |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|eircom(Infonet Ireland) Limited                        |  | 100%                            |  | Provision of global data services                                        |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    
|                                                       |  |                                 | 
|GoFree Limited                                         |  | 100%                            |  | Property investment company                                              |  | 114 St. Stephen's Green West, Dublin 2, Ireland.                    



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|                        |  |     |  |                                       |  |                                                                         
|----------------------- |  | --- |  | ------------------------------------- |  | ------------------------------------------------------------------------
|Associated Undertakings |  |     |  |                                       |  |                                                                         
|                        |  |     | 
|Altion Limited          |  | 33% |  | Telecommunications software solutions |  | AIB Investment Building, Percy Place, Dublin 4, Ireland.                
|                        |  |     | 
|Buy4Now Limited         |  | 22% |  | E-commerce software developer         |  | 9 The Mall, Beacon Road, Sandyford Industrial Estate, Dublin 18, Ireland