Rare-earth-deficient R 1−x Ni 2 Laves phases, which reportedly crystallize in a C15 superstructure with ordered R vacancies, have been investigated by perturbed angular correlation ͑PAC͒ measurements of electric quadrupole interactions at the site of the probe nucleus Cd resides on the cubic R site, a strong axially symmetric quadrupole interaction ͑QI͒ with frequencies q Ϸ 265-275 MHz has been found in the paramagnetic phases of R 1−x Ni 2 with R = Pr, Nd, Sm, Gd. This interaction is not observed for the heavy R constituents R = Tb, Dy, Ho, Er. The fraction of probe nuclei subject to the QI in R 1−x Ni 2 , R =Pr,Nd,Sm,Gd, decreases from 100% at low temperatures to zero at T Ͼ 300 K and 500 K for R = Sm, Gd and R = Pr, Nd, respectively. At T = 100 K the QI is static within the PAC time window, but at T = 200 K fluctuations with correlation times C Ͻ 10 −6 s, have been detected. These observations can be explained consistently by two assumptions: (i) the mother isotope 111 In of the PAC probe 111 Cd constitutes an attractive potential for vacancies and (ii) the R vacancies in R 1−x Ni 2 are highly mobile at temperatures T Ͻ 300 K, which is incompatible with a static vacancy superstructure. The measurements indicate a decrease of the vacancy-probe binding energy from the light to the heavy R constituents of R 1−x Ni 2 . For R = Pr, Nd, Sm, Gd the binding energy is in the range 0.15-0.40 eV. The activation energy E A for vacancy jumps near the probe derived from the temperature dependence of the nuclear spin relaxation at 200 K ഛ T ഛ 300 K is small. The values observed in different samples cover a range of 0.1 eVഛ E A ഛ 0.23 eV. The trial frequency w 0 of these jumps appears to be correlated to the activation energy: ln w 0 ͑MHz͒Ϸ58E A ͑eV͒. At high temperatures T Ͼ 500 K nuclear spin relaxation related to vacancy hopping is observed in nearly all R 1−x Ni 2 . Auxiliary