PCT filings fell by 4.5% in 2009, according to figures published by WIPO this week.
The decline was most pronounced among filers in Europe and the US, with an 11.4% fall in the US and 11.2% decline in Germany.
But filings from China grew by 29.7%, making the country the fifth largest PCT user. Filings from Japan and Korea also rose.
Panasonic regained its place at the top of the list of PCT applicants, with 1,891 applications published in 2009. Huawei was second, followed by Bosch, Philips and Qualcomm.
The general decline in PCT filings in the past year is likely to be linked to the economic recession.