Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around Z=82 and the neutron mid-shell at N=104.Purpose: Evidence for shape coexistence has been inferred from α-decay measurements, laser spectroscopy and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements.Method: Secondary, radioactive ion beams of 202Rn and 204Rn were studied by means of low-energy Coulomb excitation at the REX-ISOLDE facility in CERN.Results: The electric-quadrupole (E2) matrix element connecting the ground state and first-excited 2+1 state was extracted for both 202Rn and 204Rn, corresponding to B(E2;2+1→2+1)=29+8−8 W.u. and 43+17−12 W.u., respectively. Additionally, E2 matrix elements connecting the 2+1 state with the 4+1 and 2+2 states were determined in 202Rn. No excited 0+ states were observed in the current data set, possibly due to a limited population of second-order processes at the currently-available beam energies.Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.Read less <