Method

Diagnostic Selling is not consultative selling

I hear it regularly: "Isn't what you do just consultative selling?" The answer is no. And the difference is bigger than it looks.

Greg Trinidad · 6 min read · October 2026

The comparison is understandable. When people first see Diagnostic Selling, they see a salesperson who does not start with a pitch. Who asks questions, listens and only proposes something later. A consultative seller does that too. So does a SPIN salesperson. And so does someone trained in solution selling. From the outside, they all look like variations on the same idea: ask first, then sell.

But it is not about whether you ask questions. It is about what you want to establish with those questions, and what you are allowed to do afterwards.

What consultative selling does

Consultative selling was described by Mack Hanan in 1970. The salesperson acts as an adviser: they map the customer's needs and goals and recommend the solution that fits best. That was a big step forward from the salesperson who simply promoted their product.

The central question of consultative selling is: what does this customer need? If you understand that well, you can give fitting advice. And fitting advice leads to a sale.

That is exactly the assumption Diagnostic Selling does not make.

A need is not enough

A customer can need something and still not decide. You see it in every pipeline: deals where the need is clear, the proposal is right and the price is reasonable, and which have still been stalled for months.

Diagnostic Selling therefore asks a different question. Not: what does this customer need? But: which condition for a responsible decision is still missing? There are three:

• Stake, why him: what does this person notice themselves if the problem persists?
• Trust, why you: can they carry the risk of choosing you, and of being held accountable for it later?
• Urgency, why now: what happens if they leave this as it is for another year?

If one is missing, nothing happens. However good your advice.

Consultative selling asks what the customer needs. Diagnostic Selling establishes why they are not yet deciding.

And SPIN, Challenger and solution selling?

The same confusion arises with three other well-known methods. Each has its own strength. None of the three asks the question Diagnostic Selling asks.

SPIN Selling

Neil Rackham published SPIN Selling in 1988, based on research into sales conversations. It is a four-step questioning technique: Situation, Problem, Implication and Need-payoff. The aim is for the customer to start stating the value of a solution themselves. That works well in a conversation. But it remains a technique for leading the customer towards a solution, not a way of establishing whether a decision is responsible now.

The Challenger Sale

In 2011, Matthew Dixon and Brent Adamson described the Challenger salesperson: someone who teaches the customer something new about their own business, tailors the message to the person in front of them and takes control. Diagnostic Selling deliberately does not begin by persuading, presenting or quoting. The first thing you do is establish what is missing. A strong insight does not solve a lack of Trust or Urgency.

Solution selling

Solution selling emerged in the 1980s. The salesperson looks for the customer's pain and sells not a product, but a solution to that pain. Pain matters. But pain without personal Stake, without Trust in you and without Urgency does not lead to a decision. Then you have a customer who acknowledges the problem and still does nothing.

Selling nothing is a valid outcome

The biggest difference lies in what is allowed to happen after the questions. In most methods, the conversation is designed to work towards a purchase. A no is then a lost deal.

In Diagnostic Selling, the diagnosis determines the smallest justified next step, including the option to wait, to stop or to sell nothing. That is literally in the definition, and it is not a side issue. If Urgency is missing, you do not create it with a deadline or a temporary discount. You agree when you will look again, and you stick to it.

That also changes what success means. Success is not "deal closed", but "responsible decision made". Sometimes that is a yes. Sometimes it is a no.

Not a conversation technique, but a design model

Consultative selling, SPIN, Challenger and solution selling are mainly about the sales conversation and the sales process. Diagnostic Selling is also a design model for the sales organisation. The same question runs through the entire commercial chain: from demand generation and qualification to connection, baseline measurement, confirmation, explicit agreement, contract, onboarding and aftersales.

That is why a Digital Sales Consultant does not only work on better conversations. They investigate why customers do or do not reach a decision, and help organisations shape their commercial processes accordingly.

Why the distinction matters

You could dismiss this as a debate about names. But the difference has consequences. If you think you are doing consultative selling, you look for better advice or a better proposal when a deal stalls. If you work diagnostically, you first ask what is missing. Those are two very different next steps.

Want to see the methods side by side? The full comparison puts them in one overview. The method itself is set out in De Vuurdriehoek and Diagnostisch verkopen, with part I of both free to read.