Exhibit 8.1

Significant Subsidiaries and Investees

The following table sets forth our
significant subsidiaries and investees accounted for using the equity method at December 31, 2010:



|                                                    |  |                              |          |  |                                           |  |        |             |  |                                                                                                                                                                                                                                                                                                             
|--------------------------------------------------- |  | ---------------------------- | -------- |  | ----------------------------------------- |  | ------ | ----------- |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Name of Company                                     |  | Jurisdiction ofestablishment |          |  | Percentage ofownership andvoting interest |  |        | Description
|                                                    |  |                              |         
|Subsidiaries                                        |  |                              |          |  |                                           |  |        |             |  |                                                                                                                                                                                                                                                                                                             
|                                                    |  |                              |         
|Integración de Servicios TMX, S.A. de C.V.          |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Intermediate holding company.                                                                                                                                                                                                                                                                               
|                                                    |  |                              |         
|Alquiladora de Casas, S.A. de C.V.                  |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Real estate company owning our facilities.                                                                                                                                                                                                                                                                  
|                                                    |  |                              |         
|Compañía de Teléfonos y Bienes Raíces, S.A. de C.V. |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Real estate company owning our facilities.                                                                                                                                                                                                                                                                  
|                                                    |  |                              |         
|Consorcio Red Uno, S.A. de C.V.                     |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Supplier of telecommunications network integration services and information systems.                                                                                                                                                                                                                        
|                                                    |  |                              |         
|Teléfonos del Noroeste, S.A. de C.V.                |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Fixed-line public network concessionaire for the state of Baja California Norte and the San Luis Rio Colorado region of the state of Sonora.                                                                                                                                                                
|                                                    |  |                              |         
|Uninet, S.A. de C.V.                                |  |                              | Mexico   |  |                                           |  | 100.0% |             |  | Provider of corporate networks and Internet access services to Telmex and corporate customers.                                                                                                                                                                                                              
|                                                    |  |                              |         
|Telmex USA, L.L.C.                                  |  |                              | Delaware |  |                                           |  | 100.0% |             |  | Authorized long distance service re-seller, provider of prepaid telephone cards and payment collection services for lines in Mexico (installation and monthly rental), and authorized
by the FCC to provide facility-based long distance services, data transmission and cross-border data transit services.
|                                                    |  |                              |         
|Affiliated companies                                |  |                              |          |  |                                           |  |        |             |  |                                                                                                                                                                                                                                                                                                             
|                                                    |  |                              |         
|Grupo Telvista S.A. de C.V.                         |  |                              | Mexico   |  |                                           |  | 45.0%  |             |  | Provider of telemarketing services in the United States and Mexico.