The application relates to a hearing assistance device and to a method of performing a real ear measurement. The method comprises providing a first controlled acoustic feedback path from an output transducer to a measurement input transducer via a standard acoustic coupler; generating a first probe signal; estimating and storing a first estimate of the first controlled acoustic feedback path; and providing a second controlled acoustic feedback path from the output transducer to the measurement input transducer via the residual volume between the ITE part of the hearing aid device and the user's eardrum; generating a second probe signal; estimating and storing a second estimate of the second controlled acoustic feedback path; and determining a real ear to coupler difference from said first and second acoustic feedback estimates. An alternative and relatively simple method of determining an RECD-value in hearing assistance device of a particular user is thereby provided.