PurposeThis study analyzes the factors behind the decisions made by the largest listed Chilean companies that mandatorily adopted the International Financial Reporting Standards (IFRS) in 2009 to present comparative IFRS financial statements that year. The authors focus on the role of the expected impact of the change in the accounting standards on a company's financial position as a determinant of this decision.Design/methodology/approachThe sample comprises 105 nonfinancial companies, of which 57 decided to present comparative IFRS financial statements (full adoption) and 48 did not (proforma adoption). Logistic regression is employed to model the decision of interest.FindingsThe decision for full adoption is positively associated with the company's expectation that the change in the accounting standards would improve its financial position, albeit only up to a certain threshold, as evidenced by their inverse U-shaped association.Originality/valueIFRS adoption in Chile creates a unique scenario that allows us to contribute to the literature on the determinants of voluntary disclosure by focusing on a specific case in which the decision to disclose comparative financial statements is associated with mandatory IFRS adoption. The present study provides evidence that opportunistic behavior influences this decision.