I Wonder Why by Showaddywaddy first appeared on the Israeli foreign-music chart on 23 Apr 1978, entering at #27. It peaked at #17 on 7 May 1978. In total it spent 5 weeks on the chart, last charting on 21 May 1978.
| Wk | Date | Pos |
|---|---|---|
| 1 | 23 Apr 1978 | 27 |
| 2 | 30 Apr 1978 | 22 |
| 3 | 7 May 1978 | 17 |
| 4 | 14 May 1978 | 17 |
| 5 | 21 May 1978 | 28 |