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 2004.  Name
  
  Proportion of
  Share Capital Held
  
  Nature of
  Business
  
  Registered Office and
  Country of IncorporationPrincipal Subsidiary UndertakingsValentia
  Telecommunications (unlimited public company)
  
  100%
  
  Holding
  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.eircomFunding (unlimited public
  company)
  
  100%
  
  Financing
  company
  
  114
  St. Stephens Green West, Dublin 2, 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.Eirtrade
  Services Limited
  
  100%
  
  Provision of
  electronic trading services
  
  114 St.
  Stephens Green West, Dublin 2, Ireland.Indigo Group
  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.Continuous
  Communications Systems Limited
  
  100%
  
  Communications
  contractors
  
  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.Topsource
  Recruitment Limited
  
  100%
  
  Employment
  agency
  
  114 St.
  Stephens Green West, Dublin 2, Ireland.eircomNet BV
  
  100%
  
  Investment
  holding company
  
  Strawinskylaan
  3105 1077 ZX, Amsterdam, The Netherlands.  
   Name
  
  Proportion of
  Share Capital Held
  
  Nature of 
  Business
  
  Registered Office and
  Country of IncorporationeircomInternational Networks
  Limited
  
  100%
  
  Provision of
  telecommunications and related 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.Associated Undertakingseircom Enterprise Fund Limited
  
  50%
  
  Seed capital
  company and early stage fund company
  
  114 St.
  Stephens Green West, Dublin 2, Ireland.Beacon
  Integrated Solutions Limited
  
  49%
  
  Information
  technology consultancy
  
  Howleys
  Quay, Limerick, Ireland.Telecom
  Engineering Services Limited
  
  35%
  
  Telecommunications
  engineering services
  
  Unit 14,
  Cherry Orchard Industrial Estate, Dublin 10, Ireland.Altion TI
  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