The measurements of geometrical distribution of thermal neutron flux in research reactors are often used in the field of reactor operation and reactor physics. Usually such measurements are carried out by using the gold wire activation method. This method has been used for measuring a thermal neutron flux at the location of a Cobalt Irradiation Device (CID) of ETRR-2. A special device was used for locating samples in an irradiation box and the measurements were performed for seventy-two positions. The Monte Carlo MCNP-4B code has been used for the modeling and simulation of ETRR-2 core with structural materials and surrounding beryllium reflectors. The device used in the flux measurement was also simulated in the MCNP-4B model. The thermal flux has been calculated and compared with the experimental one. The results show good agreement between the measured and calculated flux.