Quantum Monte Carlo approaches such as the diffusion Monte Carlo (DMC) method are among the most accurate many-body methods for extended systems. Their scaling makes them well suited for defect calculations in solids. Parker, Wilkins and Hennig (pp. 267–274) review the various approximations needed for DMC calculations of solids and the results of previous DMC calculations for point defects. They present estimates of how approximations affect the accuracy of calculations for self-interstitial formation energies in silicon. As shown on the cover image, including the corrections for the approximations yields DMC values for the X, T and H interstitial defects in silicon on par with the GW and hybrid-functional DFT (HSE) calculations. This Feature Article is part af the article series “Advanced Calculations for Defects in Solids – Electronic Structure Methods” (guest edited by A. Alkauskas, P. Deák, J. Neugebauer, A. Pasquarello, and C. G. Van de Walle) which is being published in the issues of physica status solidi (b) during 2011.