The isothermal and non-isothermal viscoelastic flow of Phan-Thien-Tanner (PTT) fluids is considered in lid-driven polar cavity geometry, using a numerical solution method with parameter continuation technique. Thermoelastic effects, in terms of elastic/elongational effects and viscous dissipation, are demonstrated by the changes in vortical structure, temperature/stress distributions and heat transfer characteristics in the curved cavity. Central vortex/maximum temperature location shifts are observed under elastic and elongational (strain hardening and strain softening/shear thinning) effects for isothermal and non-isothermal conditions. The growth in size and strength of a secondary vortex is denoted in the downstream stationary corner of the cavity for the viscoelastic fluid under strain hardening, which also introduces an increase in stress gradients. Viscous heating is observed with elongational effects near the central vortex in the cavity. Stress components and their gradients decrease under viscous dissipation. The changes in temperature field and heat transfer properties in the cavity are revealed.