The positron annihilation and acoustic methods were applied to investigate solvation of potassium iodide, and tetra-n-butylammonium iodide in methanol. The acoustic results show that the influence of KI on the structure of liquid is stronger but shorter in their range than that Of (C4H9)(4)NI, although the solvation numbers are lower for KI. The solvation numbers of ions (five for K+, seven for (C4H9)(4)N+ and two for I-) are deduced. The positron annihilation suggests that the effect of KI on liquid methanol structure is stronger but shorter in range, leading to formation of small but more compressed solvates. (c) 2007 Elsevier B.V. All rights reserved.