The detection of a high conductivity anomaly below the northern (Bolivian) part of the Altiplano-Puna plateau motivated a new analysis of magnetotelluric (MT) data which were formerly collected further south in NW Argentina. After appropriate dimensionality analysis from a profile located in the magmatic arc and backarc of the south-central Andean subduction zone, two-dimensional (2-D) electrical conductivity modelling of the crust and upper mantle in the eastern sector could be performed, i.e., in the eastern Puna and backarc zone. The 2-D conductivity models show a conductive zone beneath the eastern Puna shoshonitic volcanoes and nearby Tuzgle volcano, which reaches from the upper crust to the upper mantle. We suggest that this conductor is related to the Puna volcanism of enriched mantle composition. Whether the western Puna is also characterized by anomalous conductivities at crust-mantle depths, is still an open question. ¿ 2001 American Geophysical Union