Almost one in 10 people in Wales referred for urgent cancer treatment by their GP wait longer than two months to be seen by specialists, figures show.
All patients referred by a GP should be seen within two months
But those seen within the two-month target rose from 86% in January to March to 91% during April to June.
The Welsh Assembly Government said it was disappointed targets were not fully achieved, but noted improved figures.
Simon Blackburn, of Macmillan Cancer Support, said the headline figures may be misleading.
He told BBC Radio Wales: "I've noticed that the figure being released of 91% is actually an average and Macmillan and others would share the concern that behind that average are some more worrying figures.
"Of particular concern for Macmillan are the lung, head-and-neck neurological figures.
"The head-and-neck figure is actually 66%, which is pretty poor, and for cancers where the survival rates and the journey that the cancer patients go on can be more problematic, it's clearly vital that people receive treatment as soon as possible."
However, the cancer charity Tenovus said it was "encouraged" by the overall results of the latest waiting times, despite them "falling short of the ideal".
Tenovus said: "With the number of cancer cases diagnosed rising each year and the current limited resources available for cancer services, these figures have to be commended.
"As with any patient-related issues there will always be room for improvement and these figures highlight the need for further funding into cancer screening and diagnostic facilities, as well as treatment delivery."
The Welsh Assembly Government said it was "disappointed that the cancer wait targets published today for the end of June are not being fully achieved".
It added: "The assembly notes, however, that the latest statistics show an improvement in meeting the standards of treatment compared with the previous quarter."