Temperature dependent positron lifetime measurements in Y1-xPrxBa2Cu3O7-δ are discussed, and reveal positron trapping at low temperature (T<400K) and for small x. Therefore YBa2Cu3O7 was measured by 2D-ACAR at T=450K, showing clearly the 'pillbox' Fermi surface. We also studied in detail the 3D 'ridge' Fermi surface in DyBa2Cu3O7-δ and compared it with theory. In oxygen deficient YBa2Cu3O7-δ, the ridge disappears for increasing δ without change in width, which is consistent with the phase separation model of Mesot et al.