With the number of ACT participants in the scheme tipped to grow rapidly during the second half of the year, the advocacy groups said pre-planning and knowledge of what was on offer made a crucial difference to outcomes.

People With Disabilities ACT executive officer Robert Altamore, who has been blind since birth, said the NDIS had made a major positive difference to those people who had been able to navigate through it.

"Some participants are getting better outcomes than others, and that is directly attributable to the quality of planning and quality of advocacy they get," he said.

"If you don't know what's there you can't get it."

ACT Disability, Aged and Carer Advocacy Service chief executive Fiona May said her organisation wanted a commitment from the ACT government it would continue to fund advocacy beyond June next year and increase amounts as demands grew.

She also called for increased federal funds for advocacy.

The service was now helping several unhappy participants seek internal review of decisions by the National Disability Insurance Agency refusing access to early intervention supports in plans.

Ms May said one person had also sought help to challenge an agency decision in the Administrative Appeals Tribunal, the first Canberran to do so.

"In a big and complex plan there can be 50 [funding] decisions," she said.

"Probably the majority of people are happy with most of the decisions, but there are families who were accessing the early intervention supports and that pathway has been interrupted by the NDIS."

The most recent agency report, for the December quarter, found 95 per cent of participants surveyed nationally rated their NDIS experience as good or very good, although a citizens' jury report released last week raised concerns about gaps in ACT services.

There were 434 ACT participants who had a plan approved in the first six months of the scheme.

December was the busiest month; about 130 plans were approved.

The average package in the ACT cost nearly $50,000 in December, above the national average of $35,300 for the scheme's first 18 months.

Mr Altamore, a former federal government lawyer, said he had begun his own application for a plan last month, seeking services including orientation and mobility training.

A Community Services Directorate spokesman said a working group made up of the Commonwealth and all jurisdictions was developing a new National Disability Advocacy Framework which was expected to be completed by the end of this year and would guide the NDIA's funding of advocacy services.