Four convenience samples comprising customers of two IKEA stores, one in England the other in Norway, were obtained for the purpose of investigating willingness to pay (WTP) for an environmental attribute through certification and eco-labelling. Two survey-based valuation methods were applied in each store: conjoint analysis (CA) and contingent valuation (CV). In the sample of English IKEA customers responding to CA questions, extra median WTP for the eco-labelled alternative was 16% of the price of the existing unlabelled alternative. In the sample responding to CV questions, median estimate of the price premium was 7.5%. In the samples of Norwegian IKEA customers, the CA median was 2%, while the CV median was 6%. Only in the English cases did the relation between CA and CV estimates turn out as expected.